The inclusion of Mariano Rivera, Roy Halladay and Edgar Martinez in this year's Hall of Fame class is a reminder that sometimes good things take time.
Rivera was a failed starter, and, though it's hard to fathom now, he actually blew three of his first six save opportunities when the Yankees made him their closer in 1997. Halladay was demoted to Class A to rebuild his delivery after a brutal sophomore season. Martinez's career didn't truly blossom until he became a full-time designated hitter in his age-32 season.
In that spirit, let's go over a list of guys who have had iffy starts to their careers, but are still worth believing in.
To be clear, we're not suggesting any of these guys are going to be Hall of Famers, but they are all capable of bigger things than we've witnessed to date.
J.P. Crawford, Mariners
The bloom is off the rose for the former Phillies top prospect, with the team moving on from Crawford just 72 games into his big league career by trading him to Seattle for Jean Segura. There are a lot of concerns about what we've seen from Crawford in that small sample. He's hit just .214 with a .692 OPS and graded out poorly on the defensive end. Those concerns are coupled with an uninspiring .244 average and .713 OPS in 230 games at the Triple-A level.
But the 24-year-old Crawford could emerge as a change-of-scenery type with less pressure placed upon him in Seattle. Crawford dealt with a forearm strain and hand fracture that contributed to his nine errors in '18. He maintains the range and arm strength to become a dynamic defender at a pivotal position. And offensively, he draws walks (12.4 percent walk rate in the bigs) and still has power potential.

Julio Urias, Dodgers
It's not Urias' fault that we all wanted him to arrive at 19 years old and instantly become the next Fernando Valenzuela. Nor is it his fault that he sustained an injury that required the Tommy John of shoulder surgeries, an anterior capsule procedure with a low success rate.
But time was and is on Urias' side. He's 22 years old. He came back at the tail end of last season with his velo intact and pitched some important innings out of the 'pen in the postseason. His innings will be limited this year, his long-term role is an open question, and he'll likely never reach the ceiling he would have hit had the shoulder issue not intervened. But Urias can still be a major weapon on that L.A. staff.

Yoan Moncada, Reynaldo Lopez and Lucas Giolito, White Sox
Though the Sox's attempts to turn a corner could potentially involve the signing of Manny Machado or Bryce Harper, not even an "A" free agent can push this club into contention independent of young players reaching their potential. Thankfully, there are still several candidates to do just that.
Lopez, 25, has graded out as basically a league-average arm in his first 280 innings in the bigs, and there's value just in that. But there were flashes of true front-line potential in '18, culminating in a 1.09 ERA and 3.89 strikeout-to-walk ratio in five September starts.

His Adam Eaton trade mate Giolito, 24, had the dubious distinction of the highest ERA in baseball among qualified starters, but he, too, made some second-half strides -- namely, improving his strike-throwing percentage from 58.4 to 62.9.

The Sox envisioned Moncada as a lineup linchpin when they got him in the Chris Sale trade, but so far he's struck out in one-third of his big league plate appearances.

Still, he'll be just 24 in 2019, and his hard-hit percentage increased from 35.2 in 2017 to 44.1 last year. If he can cut down on the K's, he can still emerge as a big-time bat.
Byron Buxton and Miguel Sano, Twins
The Twins are the other team that can make the AL Central interesting this season if some former hot prospects finally attain consistency at the Major League level.
Unlike the others on this list, there's no projection with this pair. We've already seen what both can contribute -- Sano with his monstrous second half in his rookie year of '15 and All-Star-worthy first half of '17, and Buxton with his MVP-level second half of '17.

Alas, both were busts last season, beset by injury and struggles that led to Minor League demotions. But both are also just 25. With better strike zone judgment from Buxton and better conditioning from Sano, they can still become stars.
Manuel Margot, Padres
Margot was the key to the deal that sent Craig Kimbrel to the Red Sox, but, more than 1,000 plate appearances into big league life, he has a .697 career OPS.
At the moment, the Padres have a bit of an outfield logjam, and Margot could find himself in a fight for center-field at-bats with Franchy Cordero. But Margot did cut down on his strikeouts in 2018, and any further offensive refinement would allow him to take better advantage of his elite sprint speed. He remains a potential 30-stolen base guy in a game that doesn't have many of those.

Austin Meadows and Tyler Glasnow, Rays
These guys were still well-regarded enough to make up two-thirds of the package the Pirates sent to the Rays for Chris Archer. But just as Archer's trade value had become difficult to predict given his up-and-down big league track record, the values of Meadows and Glasnow took a hit as they tried to find their footing in their first exposures to the Majors.
Meadows struggled a bit in the Minors in '17 (.261/.323/.384 slash across three levels) and didn't earn a call-up. Then he thrived in the bigs early in '18, only to cool down and endure another demotion mid-year. But in '19, he has the chance to emerge as the Rays' everyday right fielder, and it will be interesting to see what the 23-year-old does with the opportunity.

Glasnow, once widely regarded as one of the top pitching prospects in the game, has compiled just south of 200 innings in the big leagues, mostly out of the Pirates' bullpen. But the Rays put him back in the rotation, and he responded with a 4.20 ERA in 11 starts. What's encouraging is that the Rays helped Glasnow harness some control issues (his walk rate dropped from 14 percent to around 8 percent), and he's developed a new slider. He's just 25.

Clint Frazier, Yankees
He arrived to the Yankees in the 2016 Andrew Miller trade with that bright red hair and future. Frazier's outgoing personality screamed future star, but his first manager in the Yankees' system, Al Pedrique, took things a step further by comparing him to a young Michael Trout. When Frazier arrived to the bigs in 2017 and instantly churned out some huge hits, it was fair to wonder if Pedrique was onto something.
Then came the league adjustment. Then an oblique injury. Then a concussion last spring that sapped a lot of his 2018 development time. Now, it's hard to know if or when Frazier will slot into the Yankees' outfield this season. (He could compete with Brett Gardner in left field this spring, but it would surprise no one if the Yanks defer to the vet.) But having recently been cleared to return to baseball activities, he's definitely one to watch.

Bradley Zimmer, Indians
A former first-round pick, Zimmer is now 26 with 446 plate appearances that have resulted in a 38.6 percent strikeout rate, a .671 OPS and a demotion back to Triple-A last year. What's more, while back at Columbus, his vigorous style of play resulted in a shoulder injury that required surgery last summer, so his timeline to return to the Majors is up in the air. 
But barring some major acquisition between now and Opening Day, the Indians' outfield is awash in opportunity for a player with Zimmer's upside. He has the speed and defensive ability to change games. He just needs to harness his aggressiveness in the field and improve his contact at the plate.

Orlando Arcia, Brewers
So much went so well for the Brew Crew in '18. Not this. Arcia had shown potential with 15 homers and 14 steals in 2017, but his offensive struggles (.236/.268/.307) necessitated two demotions to Triple-A last season.
There were some positives, though. For one, Arcia is an impact defender at shortstop. And when he returned from his second stint in Triple-A, his line-drive rate improved from 13.9 to 25.9, and he hit three big homers in the postseason. His Minor League track record insists the disaster that was his first half in '18 is probably an outlier.