It’s been a complicated two years for Amed Rosario. Entering the 2017 season as one of the top prospects in the game, his debut was a letdown given both his pedigree and the anticipation surrounding his long-overdue promotion. But while 2018 was in many ways still a struggle for the young shortstop, a mediocre set of season stats belie some glimpses of the star many believed he would become.
Even accounting for an elite defensive position and excellent baserunning, there’s no question that the .256/.295/.381 line Rosario ended his 2018 with is uninspiring. That 85 wRC+ was just enough to edge him towards an average major leaguer per Fangraphs (1.5 WAR), but Baseball Reference took a sour view of his defense and gave him a barely-over-replacement-level 0.6.
Some rays of hope have emerged, though. Between 2017 and 2018, Rosario cut his strikeout rate from nearly 30% to just over 20% - below league average. At the same time, he raised his walk rate from an unthinkable 2% to close to 5%. It’s still a major flaw in his game, but a significant achievement nonetheless, and one that indicates the 23 year old’s game is still developing.
The course of Rosario’s 2018 season also showed a positive trajectory, with a more-than-serviceable .284/.318/.413 line across 239 plate appearances in August and September with 17 extra base hits and 15 stolen bases (notably, this was right around the time Jose Reyes stopped getting regular spot starts in his stead).
It’s perhaps not fair to Rosario to expect him to pick up right where he left off, but it also wouldn’t be entirely surprising if he did. If you believe that is the real Rosario, and that his poor defensive metrics from 2018 were an exception rather than a rule, you’re looking at a true breakout for 2019, and a foreshadowing of even more from his peak two or three years down the line.
Projection systems are generally in agreement with one another on Rosario, and see him splitting the difference between his overall season line and his strong finish. ZiPS expects a .266/.303/.401 year, Steamer a similar .262/.304/.391, and PECOTA a modestly more pessimistic .252/.229/.385.
Any one of those would represent a mostly satisfactory outcome for Rosario, though not the kind of breakout that would signal forthcoming stardom.
A complicating factor in anticipating Rosario’s contributions for the season is his defense. Touted in the minors as a defensive whiz, he has not yet lived up to that reputation via the eye test and his defensive metrics lag behind even further. The dangers of reading into a single season notwithstanding, DRS had him at an atrocious -16 last year and Baseball Prospectus’s -6.6 Fielding Runs Above Average doesn’t look much better.
How much of this is genuine struggles as opposed to the fluctuations of imperfect defensive metrics or a laser-focus on his batting at the expense of all else? That’s very difficult to say at this point, though this season will be an informative one at least in regards to increasing his sample size. Suffice to say, the standard for his unequivocal success at the major league levels is going to look very different if his glove doesn’t take another step forward.
With just over a full season’s worth of plate appearances and a mere 23 candles on his birthday cake, it would be jumping the gun to say this is a do or die season for Rosario. But with some positivity coming off of last season and top prospect Andres Gimenez making noise in the minors, it’s as good a time as any for him to establish his role as part of the Mets’ talented young core.