Predicting breakout seasons is the holy grail for front-office executives and fantasy baseball players, one of baseball's most profitable prognostication challenges. The 2018 season will have its own Justin Smoaks and Yonder Alonsos, players who significantly improved their outlooks for at least a time, but identifying those players is a tricky proposition.
Projection systems see things in millions of seasons, but we only get exactly one 2018. ZiPS, for instance, can spit out a projection that tells me Corey Seager has a 4.2 percent projected shot at hitting 40 homers, the best percentage for any player who hit fewer than 25 in 2017, but it can't tell me whether 2018 will be one of the 95.8 percent of years in which he falls short of that total. Still, being hard isn't an excuse, so let me run down some of the breakout candidates with the most interesting upside in the season to come.
OF Christian Yelich, Miami Marlins
Yelich is already one of the most valuable commodities in baseball, a star center fielder with a team-friendly contract, and if the Marlins choose to trade him, they may get more for him than they did for Marcell Ozuna and Giancarlo Stanton combined.
So what's an established star doing here? The one thing Yelich hasn't had is that crazy MVP-type season where everything goes right. He's one of the few players in baseball who can legitimately be called a .340-.350 BABIP hitter, and while he doesn't have the raw power of Aaron Judge, his average exit velocity was in the top 30 in baseball, just behind Jose Abreu and Bryce Harper. Yelich is also a solid contact hitter, and with his plate discipline and above-average contact rate, I think there's the potential to improve that strikeout rate. I think that magical year in which he has a peak Will Clark/Joey Votto season while being a center fielder is in there somewhere.
Key breakout stat: 14 percent chance of an OPS+ over 140
RHP Danny Salazar, Cleveland Indians
Salazar's ERA rose in his injury-marred 2017 to 4.28, but he actually had the best peripheral numbers of his career, adding nearly 20 percent to his already excellent strikeout rate, resulting in a career-best 3.48 FIP. Here's a list of pitchers with 100 innings in 2017 with a better swinging strike rate than Danny Salazar: Nobody. Salazar's 16.4 percent clip for swings and misses in 2017 was at the head of a top 10 that featured an impressive Cy Young candidate density: Corey Kluber, Max Scherzer, Masahiro Tanaka, Chris Sale, Robbie Ray, Clayton Kershaw, Chris Archer, Carlos Carrasco and Zack Godley. I feel pretty much the same way about Salazar now as I did about Scherzer before 2013.
Key breakout stat: 9 percent chance of an ERA + over 150
OF Joc Pederson, Los Angeles Dodgers
Pederson had a fairly miserable 2017 season, even earning him a stint for Oklahoma City (and typing that, it still feels weird that the Dodgers' Triple-A franchise isn't in Albuquerque). A lot of his offensive woes have to do with his .241 BABIP. ZiPS thinks he should have had a .296 BABIP in 2017 based on his hit ball profile and while he has underperformed the ZiPS BABIP in the past by about 15 points in his first two seasons, even a .280 BABIP would have put his OPS+ around 115-120 rather than 95.
The largest flaw in Pederson's offensive game has been his plate discipline, but his overall weak season camouflaged his progress on that front. He swung at a lower rate of out-of-zone pitches than he did in either 2015 or 2016 and set a career high for swinging at the in-zone ones. Despite a career-high in overall swing rate, his swinging strike rate dropped to 9.5 percent, actually better than the league-average, a first for him. Two years ago it was at 14 percent.
Key breakout stat: 28 percent shot at a new career high for OPS+
RHP Carlos Martinez, St. Louis Cardinals
Sure, Martinez made the All-Star game in 2017, his second in the majors, but like Danny Salazar I think C-Mart is a Cy Young candidate just waiting to happen. When he came up in the majors, he was still a raw fastball-slider guy, but he's shown steady growth as a pitcher, both in the hard sinker and a constantly improving changeup. That last pitch was in the top 10 for most horizontal movement in baseball by PITCHf/x. If Martinez can strike out 10-11 batters a game -- and I think he can -- that, plus his HR/FB rate going back to his typical level, bumps him up another tier.
Key breakout stat: 25 percent chance of 5+ WAR, 12 percent chance of 6+ WAR
3B/OF Nicholas Castellanos, Detroit Tigers
Now, I'm not talking defense here, which may be a lost cause for Castellanos. He finally had his first 20-homer season in 2017, hitting 26, but he also was 10th in baseball in Statcast Barrels, hitting only nine fewer than his former teammate J.D. Martinez, who hit 45 home runs.
Strikeout rate changes tend to be real very quickly, and it's hard to ignore the fact that Castellanos went from a 25 percent strikeout rate in the first half to 17 percent in the second; his career average is 24 percent. The 50-point half-to-half bump in batting average (.248 vs. .299) wasn't driven by any fluky changes in BABIP as you frequently see with these kinds of stark improvements or declines.
It's a small sample size for sure, but September, his best month of the season and one in which he hit .359/.377/.632, coincided with his move off third base. He always struggled as a third baseman, and while it's the kind of thing you can't say for sure is meaningful, it's enough to get me thinking. He wouldn't be the first player to have an offensive breakout after moving to a less difficult defensive position (B.J. Surhoff comes to mind first).
Key breakout stat: 42 percent chance of hitting 30+ HRs; 8 percent chance of 40+ HRs
LHP Adam Morgan, Philadelphia Phillies
Before his conversion to the bullpen, Morgan hadn't thrown a single pitch that hit 96 mph, at least in the majors. In 2017, he had four appearances in which he averaged 96 mph with his fastballs. His overall fastball velocity improved steadily as the season progressed, from an April average of 93.8 to 95.4, his best month, in September. And it got results, his contact rate improving by the second-most among pitchers with 50 innings, behind only George Knots. We haven't fully seen the improvement reflected in his ERA yet, but I suspect we will.
Key breakout stat: 22 percent shot of an ERA+ over 120
OF Nomar Mazara, Texas Rangers
Since Mazara signed at age 16 out of the Dominican Republic, scouts have raved about his power potential. He's been a popular breakout candidate in each of his first two seasons in the majors, but his power still remains more speculative, Mazara still not having a single .500 slugging percentage for a season, including in the minors.
Fundamentally, I suspect that he was called up to the majors too aggressively. While I'm a believer in challenging your most talented players, a prospect who puts up .800 OPS in Double-A may very well be an excellent offensive prospect, but not a player who is developmentally a "done deal."
Despite the learning curve, Mazara has made progress. Looking at the Statcast data for the exit velocity of pitches in the strike zone, he made great strides in 2017 at turning on pitches in the wheelhouse. We didn't see it reflected in his home run total, but he went from 13 doubles to 30, and for many young power hitters, doubles start turning into homers around Mazara's age. He's hitting fewer ground balls and also showing some improvement in the rate that he's swinging at the strike zone pitches (65 percent vs. 61 percent in his rookie season).
Key breakout stat: 26 percent shot at 30+ HRs; 4 percent shot at 40+ HRs
RHP Dinelson Lamet, San Diego Padres
ZiPS is a huge fan of Lamet, seeing him put up a league-average season for the Padres in his first full season in the majors in 2018. Lamet's walk rate is on the high side, but I suspect that reflects the fact that he's still fairly inexperienced for a 25-year-old, with only 412 ⅔ innings at all professional levels, rather than a fundamental inability to throw strikes. He actually threw strikes at a league-average rate despite 4.3 walks a game in 2017.
What Lamet is still missing is a good off-speed pitch, and while they've been working on his changeup, it remains a work in progress. As a rookie, he used it very sparingly in the majors, but if it ever clicks -- and it's a team priority -- Lamet has very real ace potential.
Key breakout stat: 17 percent shot at a 4+ WAR season