Here are ETAs for MLB's top prospects

Fifty-six prospects made Major League Opening Day rosters this season. Seventeen of those were Top 100 talents. And it hasn't stopped there either, as the D-backs proved by bringing up No. 78 overall prospect Gerardo Perdomo over the weekend.

The fun is going to continue all season long. Some will arrive in The Show early. Some will get called up later than expected. Some will jump in the line, while others will have to wait patiently (or impatiently as the case may be). You can't predict ball, as the saying goes, but let's try anyways.

The following is a month-by-month prediction of when more Top 100 prospects -- those who are not yet on Major League rosters -- will reach the bigs themselves in 2021. Within each month, players are listed by prospect rank, not expected time of promotion.

April

Jarred Kelenic, OF, Mariners (MLB No. 4)
Seattle's outfield depth already took a hit with Kyle Lewis' absence. Kelenic could have been in line for an Opening Day spot, had he not missed time this spring with a knee injury. After proving his health for a few more weeks, the M's top prospect could force the issue by the end of the month by showcasing all five tools at the alternate site and begin an expected AL Rookie of the Year candidacy.

Alex Kirilloff, OF, Twins (No. 26)
Minnesota gave the hard-hitting outfielder his Major League debut during last year's postseason, so the organization already highly values his readiness. A rough spring kept Kirilloff from winning the left-field job and forced him back to the alternate site at St. Paul. With the Twins hoping to keep pace with the White Sox all season in the AL Central, they won't be able to keep their top prospect down for much longer, even if it means leapfrogging over Brent Rooker.

May

Wander Franco, INF, Rays (No. 1)
Franco just turned 20. He hasn't technically played above High-A yet. He probably wouldn't play his natural position of shortstop. We get it. He is still the best prospect in baseball and was on the taxi squad for the World Series of all things last year. The Rays know what they have in him, and it's a potential 80-grade hitter with plus power. The defending American League champs need to stay with the Yankees and Blue Jays in the AL East and can't afford to leave a talent like Franco's at the alternate site and Triple-A Durham for too long.

Luis Patiño, RHP, Rays (No. 19)
This is much less controversial. Patiño already has 11 Major League appearances under his belt from his days with the Padres, and the main piece in the Blake Snell return should be on call for his first trip to Tampa Bay early in the season. He is a starter long term with three above-average pitches, but after pitching out of the San Diego bullpen, he could fit any role the Rays throw at him. Kevin Cash should welcome the opportunity.

Joey Bart, C, Giants (No. 23)
Bart got 103 at-bats with the Giants last year after Buster Posey opted out. The franchise legend's return put the prospect back in the Minors to open 2021. He remains the third option on the depth chart right now, and if anything happens to Posey or Curt Casali, Bart will be in the express lane from Sacramento back to San Francisco.

Daniel Lynch, LHP, Royals (No. 29)
Kansas City's first big callup of the season ... isn't the big name some might expect after Spring Training. No matter, Lynch is the readier of the two, having reached the High-A level in 2019. The Royals were aggressive in sending pitching prospects Brady Singer and Kris Bubic to the Majors last year, and Lynch -- with his 65-grade fastball, plus slider and above-average change -- could have been there too in a 162-game season. One more month at the alternate site and a few Minor League starts could be all the 24-year-old southpaw needs to prove his case to Dayton Moore and the front office.

Spencer Howard, RHP, Phillies (No. 41)
Howard made six Major League starts with mixed results last year, and Dave Dombrowski has already said the organization plans to use him out of the bullpen to open this season. That type of transition will take some time, and it's possible the Phils want Howard to get actual games in -- not just alt-site scrimmages -- to get comfortable in the new role. His stuff still plays at the top level, and after 2020, the Phillies simply can't be without a good relief arm for too long.

Keibert Ruiz, C, Dodgers (No. 56)
Similar to Bart with less Major League experience, Ruiz got in two Major League games in 2020 and also cracked a postseason roster for the World Series champs. He remains the third catcher on the depth chart behind two good ones in Will Smith and Austin Barnes. Predicting him for a May arrival isn't so much of a prediction as it is a hedge. He could come up later if the callup is based on his performance alone, but any injuries suffered by those two and it's the 22-year-old switch-hitter who will be called upon first.

Heliot Ramos, OF, Giants (No. 80)
The 2017 first-rounder was one of San Francisco's hottest hitters this spring by showing off the above-average power that has been his trademark in the Minors. At 21, Ramos is a better hitter than Mauricio Dubón and has more of a long-term presence for the Giants than Alex Dickerson. If either trips up early and Ramos continues his 2021 mashing ways, San Francisco's No. 3 prospect should be on his way to the bay.

Shane McClanahan, LHP, Rays (No. 83)
Make that three prospects arriving this month for Tampa Bay. Again, the Rays thought McClanahan was at least bullpen-ready last postseason when they used him four times in relief. He was much the same pitcher this spring, pumping heaters in the triple-digits on occasion with a promising slider and decent change. Tampa Bay may want to get McClanahan extended through April and May, but his stuff would make him one of the most electric arms in any role for the Major League club immediately. That's saying something considering the Rays' depth of arms.

June

MacKenzie Gore, LHP, Padres (No. 6)
Many expected 2020 to be the year that arguably the game's best pitching prospect reached The Show. Command issues at the alternate site kept that from happening, and offseason moves made the San Diego rotation even more loaded now than it was before. At his ceiling, Gore belongs in the group alongside Snell, Yu Darvish and Chris Paddack, but he'll need a few weeks at Triple-A to establish that. Whether the call comes because of his own success or because the Padres' pitching depth is tested (as all clubs' depths are) will be interesting to follow.

Bobby Witt Jr., SS, Royals (No. 7)
There it is. Saying the 2019 second overall pick would make his Major League debut this season would have seemed like crazy talk in January. Then, Witt was the talk of the Cactus League after showing off a full array of skills from a premium position. Witt's time at last year's alternate site shouldn't be discounted in terms of his development, and if he looks like his Arizona self at Double-A or Triple-A, it wouldn't be a shock to see the Royals continue their aggression by summoning the right-handed slugger before the All-Star break, especially if they're competitive in the AL Central.

Matt Manning, RHP, Tigers (No. 25)
Manning was the only member of Detroit's Big Three pitchers to miss out on a Major League debut in 2020, in part because of a right forearm strain suffered in August. That injury was not a concern this spring, and a few weeks at Triple-A Toledo (where Manning still hasn't technically appeared) may be all the 6-foot-6 right-hander needs to show he can join Casey Mize and Tarik Skubal in the Motor City rotation.

Logan Gilbert, RHP, Mariners (No. 33)
Seattle only gave Gilbert one Cactus League appearance because it didn't want him getting worked up too quickly before the Minor League season starts in May. Come the second month of the Minor League campaign, however, the 2018 first-rounder should have enough gas in the tank to truly push for a spot at the next level by June. Following Kelenic's arrival, Gilbert's ascent would be another big piece of the Mariners puzzle to lock into place.

Drew Waters, OF, Braves (No. 35)
Even at his ceiling, is Waters one of the three best outfielders in the Atlanta system? Probably not, considering the current group is made up of two All-Stars and a better prospect in Cristian Pache. But it's possible Pache doesn't hit as well as would be necessary to get his Gold Glove-caliber defense in the lineup every day. Injuries are also possible, as is Waters really catching fire in his return to Triple-A, where he last played in 2019. In any case, the switch-hitting outfielder likely doesn't need much more seasoning and should be able to help Atlanta as a fourth outfielder or even more by midseason.

Nolan Jones, 3B/OF, Indians (No. 36)
Jones worked exclusively at third base this spring, but Cleveland said back in February that he could get outfield looks after that. That's his likely route to northeast Ohio as long as José Ramírez mans the hot corner in the Majors. The left-handed slugger has the plus power and plus arm to be of use for Cleveland early, and once he gets a few reps in the corner outfield spots at Triple-A Columbus, he should get the green light.

Vidal Bruján, 2B/SS, Rays (No. 49)
Back to Tampa Bay for one of the fastest prospects ranked among MLB Pipeline's Top 100. Bruján has even more of a positional issue than Franco will considering Willy Adames and Brandon Lowe are blocking his two primary positions. But his speed could translate well to an outfield spot, and as a switch-hitter, he earns plus grades for his bat as well. Working on that versatility will be key to building Bruján's case, and he should have done enough of that in the second month of the Minors.

Josiah Gray, RHP, Dodgers (No. 57)
Depth should not be an issue in the Dodgers' World Series defense; it's why they are favored to win it all again. Gray's presence at Triple-A is just a piece of that. With a good four-pitch mix and solid control, the 23-year-old right-hander could be this year's version of Dustin May and Tony Gonsolin -- a prospect who would be an easy starter elsewhere but works multiple roles in L.A. There isn't a clear path for him as of now, but the guess for our purposes is that the Dodgers find some spot for Gray by midseason, if only on a temporary basis at first.

Nick Lodolo, LHP, Reds (No. 58)
Lodolo would have had every chance to climb quickly in what would have been his first full season last year. Instead, the left-hander with three above-average pitches and plus control was stuck at the alternate site. His actual climb can begin in earnest this summer, and the Reds, who are playing in a wide-open NL Central, showed they are willing to give talent a chance when they opened the year with Jonathan India at second base. A few starts in the upper levels, and Lodolo can prove how easily he would slot into a Reds rotation that has plenty of question marks on the back end.

Brailyn Márquez, LHP, Cubs (No. 59)
The top Cubs prospect made his Major League debut last Sept. 27. It didn't go swimmingly as he was charged with five earned runs on two hits and three walks in 2/3 of an inning. That aside, it did put Márquez on the 40-man roster and one quick call-up from making The Show again. The southpaw would fit in the back of a bullpen already with an 80-grade fastball capable of touching triple-digits consistently in short spurts, and it's possible Chicago gives up on the dream of keeping him as a starter and thrusts him into that role come June.

Oneil Cruz, SS, Pirates (No. 63)
Cruz played 35 games at Double-A in 2019, spent 2020 at the alternate site and got a lengthy look with the big club this spring. He should be ready to help a Pittsburgh team with plenty of holes at some point this summer. But where will he play? Cruz played mostly short this spring, but at 6-foot-7, many evaluators think he's too big for the position. He has a cannon of an arm, but Ke'Bryan Hayes keeps him from moving to third. The likely answer is the outfield. In any case, the plus power potential and above-average speed will make the Bucs want to get a long look at Cruz as they devise their long-term strategy.

Sam Huff, C, Rangers (No. 76)
Huff missed all of Spring Training with a hamstring injury but was entering the final phases of his rehab as of last week. So long as everything continues to go well, he should be a participant in Minor League Spring Training before heading off to Triple-A. Huff showed off his trademark pop with three homers in 10 Major League games last year, and it's that slugging ability that should get him a look back in Texas once he fully re-establishes himself.

Trevor Larnach, OF, Twins (No. 78)
If not for Kirilloff, maybe we're talking about Larnach pushing for a Major League spot in April. Instead, the 2018 first-rounder is stuck a little too far down the depth chart to get an earlier call-up. That said, he is entering his age-24 season and has the above-average overall hitting ability to put pressure on Minnesota early in 2021. If injuries or ineffectiveness force the Twins to test their outfield depth further, Larnach should be ready by June to lend a promising left-handed bat.

July

Adley Rutschman, C, Orioles (No. 2)
Get ready, O's fans. This is when we expect the franchise cornerstone to be laid into place. It's absolutely likely that Baltimore will be too far out of a playoff spot for Rutschman to make a difference in the second half. It's also likely that he'll do so well in the upper levels of the Minors through May and June that they won't represent the challenge he'll need for his development. The switch-hitting backstop should at least bring plenty of value on the defensive side straight away, and if he can follow through on his plus offensive potential as well, there could be hope in Baltimore during the second half yet.

Jeter Downs, INF, Red Sox (No. 48)
Downs, who would have likely played at Triple-A for much of 2020, spent the season at the alternate site instead and will open at Worcester this time. So, he's knocking on the door already in his third organization. With above-average hit and power tools, the 22-year-old doesn't need much more seasoning but facing opposing Triple-A arms for a few months won't hurt. He'll also need to figure out a position with Xander Bogaerts holding down short. A move to second seems likeliest, allowing the Sox to use Enrique Hernández in more of a utility role.

Brandon Marsh, OF, Angels (No. 52)
The Angels outfield was loaded enough that they felt comfortable sending Jo Adell back to the Minors to open 2021. Even after Adell's struggles at the top level last season, he is still ahead of Marsh on the Halos' depth chart. But Marsh -- with four potential plus tools -- is skilled enough in his own right to find a way to Anaheim at some point during his age-23 season this summer. If Adell trips up again in his second MLB look or injuries ravage the club's depth, Marsh is a more than adequate replacement for a team with playoff hopes.

Shea Langeliers, C, Braves (No. 72)
Another 2019 first-round catcher. The Braves have Travis d'Arnaud behind the dish now and young options Alex Jackson and William Contreras on the 40-man, but Langeliers has a legitimate claim as the catcher of the future in Atlanta. His plus-plus arm and impressive framing abilities make him a Major League-quality defender right now, and the bat should hold its own. As the NL East race heads down the stretch, the bet is that the Braves will want that catching future to start in July.

Simeon Woods Richardson, RHP, Blue Jays (No. 86)
The Blue Jays made investments this offseason to make the club competitive, and it shouldn't stop at the prospect level either. Woods Richardson has four above-average pitches and impressive control heading into his age-20 season. After ending 2019 at High-A, he should be back in the upper Minors for the first half of 2021. That level of stuff should be helpful to Toronto's bullpen (arguably the club's weakness right now) or even the rotation if he isn't closing in on an innings limit.

Miguel Amaya, C, Cubs (No. 88)
This could come even earlier since Amaya is entering his third season on the 40-man roster. He also just turned 22 in March, making him young for the catching position. Amaya is at a point where he needs consistent playing time to build out his profile, especially on the offensive end, so it's possible he gets passed over if Chicago needs catching help in the first half. A July arrival would offer three months of that before getting the call to Wrigleyville, where he can try to establish himself in the next stage of the Cubs franchise.

August

Julio Rodríguez, OF, Mariners (No. 5)
A 2021 debut for a player who only turned 20 in December would be aggressive. If Rodríguez is anything like he showed last time he played in Minor League games in 2019, this might actually be conservative. The right-handed slugger has some of the most promising pop of any Top 100 prospect, and he has the promising hit tool to match. This could be a situation like Kyle Lewis in 2019, when the future AL Rookie of the Year was allowed to get his feet wet in the Majors before truly letting loose in Seattle a year later.

CJ Abrams, SS, Padres (No. 8)
Expect to hear the phrase "he's like a trade pickup" a lot in this month after the Trade Deadline. The Padres should be in the thick of the NL West race by August or at least hoping to hold on to a Wild Card Spot and adding Abrams' top-of-the-line speed and promising left-handed bat would aide in those pursuits. Yes, he plays the same position as Fernando Tatis Jr. Yes, he will be 20 for the entire season. But the Padres have been aggressive with their young talents before, and that shouldn't stop in what could be a special year.

JJ Bleday, OF, Marlins (No. 20)
Saying the Marlins have depth in the outfield might be misguided, but they certainly do have a lot of young options out there in addition to veterans like Starling Marte and Adam Duvall. At some point, the 2019 fourth overall pick is going to prove too talented to be overlooked any longer. Bleday is two years removed from leading NCAA Division I in homers, and after a year at last year's alternate site, he will get to continue to showcase that pop in the upper Minors through May, June and July. Come August, he should be banging down the door to South Beach.

Riley Greene, OF, Tigers (No. 21)
And now for the next wave of Tigers -- this time on the position-player side. The Big Three of the pitching staff having already arrived, Motor City fans can look toward the bats next, and Greene, who is expected to open the season at Double-A, could be ready by the Major League season's penultimate month. That would give Detroit a few weeks to look at its future before potentially turning the bend on its rebuild in the offseason.

Matthew Liberatore, LHP/Nolan Gorman, INF, Cardinals (No. 37, 38)
The Arizona natives were good friends well before they both were in the St. Louis organization, and it would be something if they arrived in St. Louis together. Here's how that happens. The NL Central remains as wide open as expected heading into the stretch. In order to separate themselves from the pack, the Cards turn to Liberatore as a left-handed weapon in the bullpen and Gorman as a legitimate left-handed power bat off the bench. Gorman played some second base this spring to get out of Nolan Arenado's shadow and find himself another route to meet his pal in St. Louis.

Reid Detmers, LHP, Angels (No. 73)
Evaluators expected Detmers to be one of the quickest climbers of the 2020 Draft with his polished four-pitch arsenal and good control coming out of Louisville. What do the Angels always seem to lack? Quality pitching. If the Halos want to get Mike Trout back to the postseason, they may have to turn to their top pitching prospect as a reinforcement down the stretch.

Alek Thomas, OF, D-backs (No. 79)
Arizona was willing to call up Perdomo in April, and Thomas also played at Low-A and High-A in 2019. The difference: Thomas is not yet on the 40-man roster while Perdomo was. Still, the outfielder, who turns 21 in April, is a gifted defender on the grass, a speed threat and a career .312 hitter in the Minors. If Perdomo is getting a look in 2021, so should Thomas, even if it's comparatively delayed.

George Kirby, RHP, Mariners (No. 91)
Kirby lacks Rodríguez's ceiling, but he is the pitching version of Seattle's August addition. Like the Tigers, the M's need to figure out where they stand ahead of a potentially big offseason. The 23-year-old right-hander is a control artist but also shows promising stuff with a plus heater and above-average breaking pitches. He could be a No. 3 or 4 starter for the next contender in Seattle. A few audition outings late in the season could help him secure that place.

September

Shane Baz, RHP, Rays (No. 89)
Prospect promotions in September could be even more rare as roster expansion is limited to only 28 players. That said, the Rays figure to be in the thick of either the AL East or Wild Card (or both) races and might want to make Baz this year's version of McClanahan. The right-hander can touch triple-digits with his fastball and showcases an easy plus slider. That will work in the bullpen at the tail end of his age-22 season.

Cade Cavalli, RHP, Nationals (No. 98)
The Nats are less likely to be hunting for a playoff spot come September, but it's certainly possible. (Anything is possible with Juan Soto, Trea Turner, Max Scherzer and Stephen Strasburg on the same roster, let's be honest.) If that is indeed the case, Washington could turn to their top prospect in the bullpen, where they could keep an eye on his innings at the conclusion of his first full season. Cavalli touches the high-90s and showcases three other above-average pitches. Quality relief can be the difference between just missing the playoffs and punching a ticket to October. Cavalli could be that difference in the capital.

Not placed but expected to be in MLB

Sixto Sánchez, RHP, Marlins (No. 15)
Last year's phenom looked like a lock to make the rotation out of the spring until the Marlins announced they were holding him back to build him up a little longer. Then, Sánchez was diagnosed with mild inflammation of his right shoulder on Friday, following an MRI. He is expected to rest and rehab from the injury, but until he gets back on that road in earnest, it would be a fool's errand to predict when he will return to Miami in this space. Stay tuned.

Edward Cabrera, RHP, Marlins (No. 67)
Same deal in the same organization. Cabrera suffered an inflamed nerve in his right biceps early this spring and had not yet begun throwing as of last week. Until he does, it's impossible to predict when he could crack the Majors for the first time.

Brendan McKay, LHP/DH, Rays (No. 71)
McKay underwent shoulder surgery last August. He hit some this Spring Training but was only expected to start throwing again at the end of March. When he's healthy, he could be a dual threat for the reigning AL champs. But we don't know when that will come at this stage.

Clarke Schmidt, RHP, Yankees (No. 87)
The Yankees placed Schmidt on the 60-day injured list to open the season with a right elbow strain. He is expected to resume throwing soon but hadn't officially begun that part of the rehab process as of last weekend.