After a difficult first full season at the big league level in 2018, Amed Rosario entered spring training this year with a lot of questions about his long-term role on the team. The former top prospect in baseball was coming off of a season in which he hit just .256/.295/.381 with a well-below-average 85 wRC+ in 592 plate appearances and posted just 1.5 fWAR despite playing in 154 of the team’s 162 games.
Perhaps most disappointingly, Rosario’s defensive performance did not live up to the scouting reports. While he was billed as having all of the tools needed to develop into a stellar defensive shortstop throughout his time in the minor leagues, Rosario generally struggled defensively in 2018, ranking second to last in both DRS and UZR among qualified shortstops.
Despite his struggles, Rosario was again given the starting shortstop position for the 2019 season, in the hopes that the 23-year-old would begin to show signs of getting his considerable potential to begin actualizing on the field. After a slow start to the 2019 season, Rosario began to do just that in the second half, and he showed enough tangible improvement over the course of the season to cement his place as an important part of the team’s plans at shortstop moving forward.
Rosario hit just .274/.319/.406 with a 91 wRC+ in 113 plate appearances in the first month of the season. His level of performance regressed further back to his career norms from there, as he hit just .229/.276/.422 with an 83 wRC+ in 117 plate appearances in May and .263/.283/.414 with an 81 wRC+ in 107 plate appearances in June. To make matters worse, Rosario’s defensive issues seemed to intensify during the first half of the season, to the point where a potential move to center field became a popular topic of conversation surrounding the team. Rosario made 12 errors from the start of the season through the end of June, and he committed multiple errors in four separate games between April 16 and May 4. Overall in the first half, Rosario hit .260/.299/.414 with an 88 wRC+ in 356 plate appearances, which fell closer to his 2018 line than league average.
After struggling for the season’s first three months, Rosario had easily the best month of his young career in July, hitting .350/.402/.538 with a 148 wRC+ in 87 plates appearances. While part of his torrid July was a result of an unsustainable .388 BABIP, some of the improvement could be attributed to a drastic improvement in his strikeout rate. Rosario struck out in just 12.6% of his plate appearances in July, which was a full 6 percentage points lower than his strikeout rate from June. While he did not fully maintain his elite performance from July down the stretch, the young shortstop was one of the valuable shortstops in the National League in the second half.
He ended up hitting .319/.351/.453 with a well-above-average 114 wRC+ in 299 plate appearances in the second half, and the 1.7 fWAR he posted in the second half was the third-highest total among National League shortstops, behind just Trevor Story and Trea Turner. Rosario’s defense also improved along with his offense in the second half. He committed just four errors in the second half, and while his DRS in 2019 was almost exactly as bad as it was in 2018, his -0.8 UZR put him firmly in the middle of the pack among qualified shortstops.
As a result of his second half, Rosario ended up hitting .287/.323/.432 with an almost exactly league average 100 wRC+ in 655 plate appearances on the season, and he posted 1.8 bWAR, 2.7 fWAR, and 2.3 WARP across 157 games. He ended the season with 15 home runs, 72 RBIs, and 30 doubles, all of which were career highs.
Perhaps most encouragingly, Rosario’s improvements over the course of the season appear to be backed up by improvements in his underlying contact and plate discipline stats. His lowered strikeout rate in the second half coincided with a sharp decline in his swinging strike rate, which fell from 12.7% in the first half to a well above-average 10.2% in the second half. With the decrease in swinging strikes came a sharp uptick in contact, especially within the strike zone. Rosario’s contact rate improved from 74.9% in the first half, to 80.2% in the second half, and his Z-contact rate jumped from 85% in the first half to 92% in the second, which was the seventeenth-highest rate of contact on pitches in the zone in the league in the second half.
This increase in overall contact, especially within the strike zone, and decrease in swinging strikes bodes well for Rosario’s offensive performance moving forward, and makes hitting for a high batting average more likely in the future if he can replicate it in 2020 and beyond.
After a difficult start to the season on both sides of the ball, Amed Rosario managed to have a very successful second full season in the big leagues. While it’s unclear if Rosario will ever actualize the superstar potential that scouts raved about when he was a prospect, his league average offensive performance and scratch defense at a premium position in his age-23 season should cement his place amongst the team’s young core of talented position players and keep him in the team’s long term plans at shortstop.