13 rookie hitters with big debuts in '19

We got our first look at some incredible rookie hitters this year, from record-setters like Pete Alonso to historically hyped prospects like Vladimir Guerrero Jr. to instant sensations like Yordan Alvarez.

Let's look back at some of the ones who caught our eye from the moment they first stepped on the field -- the standout hitters who made their MLB debuts in 2019.

These players flashed amazing tools, whether it was power, contact, speed, arm strength or glove work. Thanks to Statcast, we can put numbers to those tools. Statcast tracks everything that happens on the field, and it didn't miss these young guns.

Here are 13 rookie hitters who stood out in their first big league action, and the key stats that show why they could be stars to watch in 2020 and beyond.

Pete Alonso, 1B, Mets
Key stat: 66 barrels

Obviously Alonso's key "baseball card" stat is his 53 homers -- the most in MLB, a Major League rookie record and the Mets' single-season record. But "barrels" show the underlying skill set of an elite power hitter. They're balls hit with ideal exit velocity and ideal launch angle -- hit hard and driven in the air -- and so are likely to be a home run or an extra-base hit. Alonso's 66 barrels in 2019 were second most in the Majors, behind only American League home run champ Jorge Soler (70) and tied with superstars Mike Trout and Ronald Acuña Jr. Few hitters crushed the ball like Polar Bear Pete, who wasted no time hitting both the Mets' hardest homer (118.3 mph) and longest homer (474 feet) since Statcast started tracking in 2015.

Most barrels hit in 2019
1. Jorge Soler (KC): 70
2-T. Pete Alonso (NYM): 66
2-T. Mike Trout (LAA): 66
2-T. Ronald Acuña Jr. (ATL): 66
5. Nelson Cruz (MIN): 65

Yordan Alvarez, DH, Astros
Key stat: .410 expected wOBA

Alvarez didn't need to play a whole season to run away as the unanimous AL Rookie of the Year Award winner. The Astros' slugger hit 27 home runs in just 87 games and posted an incredible 1.067 OPS and a .432 weighted on-base average (wOBA), a stat for overall offensive performance, like on-base percentage, except different at-bat results are valued differently (for example, a home run is worth more than a single). Alvarez's was third best in MLB behind Christian Yelich and Trout; that should tell you all you need to know.

It was no fluke. Statcast gives every hitter an "expected wOBA" based on their contact quality -- the exit velocity and launch angle of every ball they hit. Alvarez's quality of contact was among the best of the best. His xwOBA was .410, seventh best in MLB. He was one of only 11 hitters at .400 or better, just ahead of Mookie Betts, Juan Soto, Aaron Judge and J.D. Martinez.

Highest xwOBA in 2019
1. Mike Trout (LAA): .455
2. Cody Bellinger (LAD): .429
3. Christian Yelich (MIL): .420
4. Howie Kendrick (WSH): .419
5-T. Anthony Rendon (WSH): .418
5-T. Nelson Cruz (MIN): .418
7. Yordan Alvarez (HOU): .410
MLB average xwOBA: .319

Fernando Tatis Jr., SS, Padres
Key stat: 91.4 mph average max-effort arm strength

It's a shame Tatis' debut season was cut short after 84 games. He was hitting .317 with a .969 OPS, 22 homers and 16 stolen bases in his half-season. But that's just his offense: The 20-year-old phenom was a National League Rookie of the Year Award front-runner because he was one of the most dynamic play-makers in baseball. He has it all: bat, speed, arm and athleticism.

But of all the things Tatis does ... wow, that arm. It's a cannon. Tatis' average arm strength on max-effort throws was 91.4 mph, the hardest of any MLB infielder last season, ranking ahead of players like Carlos Correa, Javier Báez and Matt Chapman. Tatis' 94.1-mph throw to get Tyler Austin on July 2 -- after a nifty play on a short hop in the hole, no less -- was the hardest-tracked putout by an infielder all year.

Vladimir Guerrero Jr., 3B, Blue Jays
Key stat: Eight balls hit 115+ mph

Vlad Jr.'s legend preceded him. The son of Hall of Famer Vlad Sr. debuted in 2019 at age 20 as one of the most heralded prospects of all time. While his rookie season had ups and downs, Guerrero certainly showed how high his ceiling is. Remember when he crushed his first two home runs on May 14? They were monster shots -- 111.3 mph and 438 feet on the first one, 113.7 mph and 451 feet on the second.

Then there's this: If you can hit baseballs 115 mph, you're on the elite fringe of exit velocity -- after all, that's 20 mph harder than the threshold for a hard-hit ball. Well, no one reached the 115-mph mark more than Vlad Jr., who ripped eight balls at least that hard during his debut season. Vlad Jr.'s 118.9-mph single on May 11 was the second-hardest batted ball by anyone in MLB all year, behind only a 120.6-mph single by Giancarlo Stanton. Impacting the ball that hard is a rare skill Vlad has. So when you look at his .772 OPS and 15 home runs in 2019, just know: There's more to come.

Most balls hit 115+ mph in 2019
1. Vladimir Guerrero Jr. (TOR): 8
2. Aaron Judge (NYY): 7
3-T. Gary Sánchez (NYY): 5
3-T. Nelson Cruz (MIN): 5
5. C.J. Cron (MIN): 4

Luis Arraez, INF/OF, Twins
Key stat: 92.1 percent contact rate

Just try to get this guy to swing and miss. A pure contact hitter in the midst of the Bomba Squad, Arraez hit .334 in his 92 games for the AL Central champs. He whiffed on fewer than one in 10 swings he took as a rookie; the 22-year-old's 92.1 percent contact rate was the best in the Majors. Arraez put the ball in play relentlessly -- in 366 plate appearances, he walked 36 times and struck out just 29 -- and made good things happen. It helps that nearly a third of his batted balls were line drives: 32.3 percent, the fourth-highest line-drive rate among the 225 hitters with 250 or more batted balls. Arraez made tons of contact, and tons of that contact was of the line-drive variety … that's the formula for a high batting average.

Bryan Reynolds, OF, Pirates
Key stat: .408 BA vs. four-seamers

Reynolds challenged for the NL batting title and finished at .314, tied for sixth in the league. He loved hitting four-seam fastballs -- the fastball of choice in MLB these days, with sinkers out of fashion. The 24-year-old switch-hitter was basically Ted Williams against four-seamers: he hit .408 against them, collecting 69 of his 154 hits and 10 of his 16 home runs. He was the only hitter over .400.

Eloy Jiménez, LF, White Sox
Key stat: 96.6 mph average exit velocity on FB/LD

Entering the year behind only Vlad Jr. and Tatis Jr. on MLB Pipeline's Top 100 prospect list, Eloy wound up leading AL rookies with 31 homers in 2019. The 23-year-old has things to work on -- he had 134 strikeouts against 30 walks, and a .315 on-base percentage -- but when he squares one up, it flies off his bat. Jiménez's average exit velocity on fly balls and line drives was 96.6 mph, the 12th highest among 175 hitters with 300 or more batted balls in 2019. He made hard contact 47.9 percent of the time, a top-15 mark in that group, and barreled the ball 12.8 percent of the time, a top-20 mark. Hard-hit fly balls and line drives? Yep, those turn into home runs, like the 471-footer Jiménez crushed on June 9, the White Sox longest of the year.

Keston Hiura, 2B, Brewers
Key stat: 50.0 percent hard-hit rate

All Hiura does is hit. The Brewers' second baseman debuted with a .303/.368/.570 slash line, .938 OPS and 19 home runs in 84 games as a rookie. And how about this: 281 hitters put at least 200 balls in play in 2019. Only nine of those made hard contact (95-plus mph exit velocity) at least half the time. And only one of those nine was a rookie. That was Hiura. The 23-year-old's 50.0 percent hard-hit rate was better than Alvarez's (48.9 percent), better than Jiménez's (47.9 percent), better than Tatis' (44.1 percent), better than Alonso's (42.3 percent). Hiura rakes.

Highest hard-hit rate in 2019
1. Miguel Sanó (MIN): 57.2 percent
2. Aaron Judge (NYY): 57.1 percent
3. Nelson Cruz (MIN): 51.5 percent
4. Kyle Schwarber (CHC): 51.2 percent
5. Franmil Reyes (SD/CLE): 51.0 percent
6. Matt Olson (OAK): 50.3 percent
7-T. Keston Hiura (MIL): 50.0 percent
7-T. Josh Donaldson (ATL): 50.0 percent
7-T. Mitch Garver (MIN): 50.0 percent
Of 281 hitters, minimum 200 batted balls

Bo Bichette, SS, Blue Jays
Key stat: 53.3 percent swing rate

Of the Blue Jays' three MLB legacies to debut in 2019 -- Vlad Jr., Cavan Biggio and Bichette -- Bichette had the most impressive numbers, just in the smallest number of games. The 21-year-old only played 46 after his late-July call-up, but he hit .311 with 11 home runs, 29 extra-base hits and a .930 OPS. Bichette doesn't get cheated. He was an aggressive hitter, swinging at more than half the pitches he saw -- 53.3 percent, placing him just outside the top 10 percent of most aggressive hitters. He also swung at the first pitch over a third of the time, putting him in the top quarter of the league. He jumped all over fastballs in particular, hitting .365 against them for 17 extra-base hits.

Cavan Biggio, 2B, Blue Jays
Key stat: 13.5 percent chase rate

Biggio showed a very different type of skill set from Bichette or Vlad Jr. The 24-year-old was extremely patient and disciplined. He swung at only 13.5 percent of pitches outside the strike zone, the second-lowest chase rate of 325 hitters who saw at least 500 out-of-zone pitches.

Lowest chase rate in MLB in 2019
1. Logan Forsythe (TEX): 11.7 percent
2. Cavan Biggio (TOR): 13.5 percent
3. Andrew McCutchen (PHI): 14.7 percent
4. Alex Bregman (HOU): 15.8 percent
5. Robbie Grossman (OAK): 16.2 percent
Of 325 hitters, minimum 500 out-of-zone pitches seen

That's good for the on-base percentage -- Biggio's was a solid .364, buoyed by a 16.5 percent walk rate that was fourth-highest among hitters with at least 400 plate appearances. His selectivity also helped Biggio make the most of his contact, even without the elite exit velocity of a Vlad Jr. -- specifically, via line drives. Biggio's 33.0 percent line-drive rate was tied for second-highest among hitters with 200 or more batted balls in 2019.

Tommy Edman, 3B/RF, Cardinals
Key stat: 29.4 feet per second sprint speed

A versatile utilityman and sparkplug on offense for the Cardinals as a rookie, Edman hit .304 with 11 home runs and an .850 OPS in 92 games for the NL Central champs. He can make a lot of things happen with his speed -- his 15 steals and seven triples speak to that. So does his 29.4 feet per second sprint speed for 2019, as tracked by Statcast. Sprint speed is a runner's average top speed on competitive runs on the bases. MLB average is 27 feet per second, and 30-plus feet per second is elite. Edman, at 29.4 feet per second, was just below the elite threshold -- and he was easily MLB's fastest third baseman. He reached the elite 30 feet per second mark on 23 individual runs.

Fastest 3B by sprint speed in 2019
1. Tommy Edman (STL): 29.4 feet per second
2. Hunter Dozier (KC): 28.3 feet per second
3-T. Kris Bryant (CHC): 28.2 feet per second
3-T. Yairo Muñoz (STL): 28.2 feet per second
5. Matt Chapman (OAK): 28.1 feet per second
MLB average: 27 feet per second Elite: 30+ feet per second

Oscar Mercado, CF, Indians
Key stat: +5 Outs Above Average

Mercado got some down-ballot AL Rookie of the Year Award votes in large part because of how he handled center field for the Tribe. As a 24-year-old rookie, he was more than capable at a premium defensive position. Mercado was worth five Outs Above Average, Statcast's metric for outfield defense based on the difficulty of all the plays an outfielder makes or misses. He made some nice catches, including four with catch probabilities less than 50 percent. And he had one of the quicker first steps in the league, by the "Reaction" component of Statcast's Jump stat for outfielders.

Aristides Aquino, RF, Reds
Key stat: 118.3 mph max HR exit velocity

OK, Aquino technically debuted in 2018 … for one plate appearance. We can squeeze the Punisher onto this list, considering he set the modern-era record for most homers through 100 career plate appearances and the NL rookie record for most homers in a calendar month. The 6-foot-4 outfielder can absolutely hammer the ball. Aquino's 118.3 mph homer on Aug. 8 was tied for the hardest in MLB in '19.

Hardest HR of 2019
1-T. Aristides Aquino (CIN): 118.3 mph (Aug. 8)
1-T. Gary Sánchez (NYY): 118.3 mph (May 3)
1-T. Pete Alonso (NYM): 118.3 mph (April 11)
4. Pete Alonso (NYM): 117.0 mph (June 20)
5. Bryce Harper (PHI): 116.4 mph (Sept. 24)

Oh, and in case you thought power was his only tool … Aquino also uncorked a 101.5 mph throw from right field in the very same game that was the hardest tracked throw by an outfielder all season.