Few pitching prospects can match Reyes' upside, but his immediate outlook is vexing. He underwent Tommy John surgery Feb. 16, 2017 and threw his first bullpen session in September. According to a study by The Hardball Times in 2014, pitchers like Reyes, who undergo the surgery between the ages of 22 and 23, experience an average return time of 15.4 months, with a 94 percent success rate (based on a sample of 143 pitchers). So while Reyes could be ready at the start of the season, it's more likely that he is not ready until May or June. Adding to the confusion is the fact that we don't know how the Cardinals plan to use Reyes in his first year back. While he is clearly a starter long term, he could spend some or all of 2018 building up his arm strength in the big-league bullpen. He is a worthy stash candidate in most formats, and while the payoff could be huge if he returns to the big-league rotation early in the first half, the risk is significant.

The Cardinals initially promoted Reyes in early August to serve as a relief ace, but poor performance and injuries in the rotation led to him receiving five starts over the season's final month. He was almost unhittable as a reliever (.138 BAA) and remained dominant as a starter, but he clearly walked too many batters in both roles. Reyes has ace-level stuff, not only dominating with his famed four-seamer that sits at 97 mph and can touch 102, but also rendering hitters helpless with highly effective secondaries in his curveball (.538 OPS against, 46.2 strikeout percentage) and changeup (.592, 34.4 percent). Fringe-average fastball command and control are the only blemishes in his profile, but his stuff is so nasty that he understandably reached the majors after just 100 combined innings at Double-A Springfield and Triple-A Memphis. Noah Syndergaard, for instance, needed 216.2 innings at those two levels before his MLB debut. Unfortunately, Reyes' development will be delayed as he is slated to undergo Tommy John surgery and miss the entire 2017 season.

A breakout candidate heading into 2015, Reyes emerged as one of the five best pitching prospects in the minor leagues last season. He posted a 2.49 ERA, 1.17 WHIP, and an eye-popping 151 strikeouts in 101.1 innings across three levels, finishing with a strong eight-start showing with Double-A Springfield. Reyes pumps gas that can touch 100 mph, but he also boasts a plus curveball and a changeup that should be average or better in time. His command is fringe average, but it does not really matter, given how nasty his stuff is. Opponents hit just .169 against him in 34.2 innings at Double-A, so his 18 walks were inconsequential. He will miss the first 50 games of 2016 after testing positive for marijuana, but that only hurts his value in single-season leagues, as he is unlikely to come up in time to make a major impact this season. However, Reyes could be a 200-K pitcher in the big leagues by 2017.

Reyes is one of the Cardinals' better pitching prospects as he's looked very good at times pitching to batters several years older than him at the Low-A level. His biggest issue has been control and that was no different in 2014; while he was less hittable he still saw his walk rate rise from 11.1% to 13.1%. Next season will be only the 20-year-old's third season as a pro and he's never looked out of place. The talent and stuff is definitely there, but he will need to harness his control issues if he wants to work his way into an MLB rotation instead of a late-innings relief role. He's proven he has the fastball to be successful in either role, striking out 137 batters in 2014 in just 109.1 innings of work. If all goes well, Reyes should finish 2015 in Double-A and be ready for his MLB debut some time in 2016.