Eddie Rosario has always been a polarizing player for me. In his first extended stint with the Twins in 2015, he showed flashes of a really exciting all round game. He was a good base runner (4.7 runs above average), a solid defender (2.2 runs above average), and clobbered 13 home runs in his age 23 season. Rosario had excelled throughout 5 minor league destinations, and was noted for having an exceptionally quick bat and hands. There were a few major problems. Rosario struck out a lot (25% in 2015, compared to a league average 21%) and he rarely walked. Like, ever. In 2015 Rosario walked just 15 times in 474 plate appearances, good for a BB% of just 3.2%, well below the league average of 8.1%. Taken together, Rosario’s strikeouts and inability to take a walk amounted to cripplingly poor plate discipline.

In 2016 some of the aspects of Rosario’s game which made him exciting disappeared. His base running regressed marginally in 2016, and majorly in 2017. His defense went from good in 2015, to acceptable in 2016, to pretty bad in 2017 (-6.2 runs above average), a dip not often discussed in the Twins heralded ‘nothing falls but raindrops’ outfield, which should be renamed to reflect the fact that anyone not named Byron Buxton is actually a poor to average defensive outfielder.

Rosario’s regression and streaky hitting were so infuriating that it led to discussion about whether he would be the odd man out in the Twins up and coming outfield moving forwards, with Buxton spectacular, Kepler solid, and Zack Granite pushing for playing time with an impressive season at Rochester. Throughout his first two seasons, Rosario had shown little progress in his plate discipline, leading folks to voice the possibility that he had hit his ceiling. Enter James Rowson.

If Pat Shurmur is the MVP of the Vikings this season, Rowson deserves the same plaudits for his work with Buxton, Polanco, and Rosario in 2017. In researching Rowson, two things seem to stand out about his approach with the young core of Twins hitters; firstly, he wants players to have a high comfort level in taking ownership of their own swings, secondly, he’s keenly aware of the strengths and weaknesses of hit hitters and publicly pushes those buttons. After a game against the White Sox, Rowson named Rosario the player of the game, despite going 0-4, crediting him for helping teammates see more pitches from Jose Quintana which eventually allowed them to force him from the game.

Rosario’s numbers from 2017 are a testament to Rowson’s work. He increased his BB% to just under 6%, taking 23 more walks than he did in 2016. Rosario’s OBP jumped almost 30 points, despite a 26 point decrease in his BaBIP from 2016 to 2017. The main cause for this increased ability to get on base? Rosario was significantly more selective with his swings in 2017. He dropped his O-Swing % (the percentage of time he swings at pitches outside the strike zone) from 42% to 37%. This decreased his overall SwStr% around 5% and led to a significantly increased Contact% (percentage of the time a hitter makes contact when swinging at all pitches). Overall, Rosario wasn’t swinging at significantly less pitches, he’s swinging at significantly more hittable ones, leading to a spike in home runs, walks, and isolated power.

Entering his final pre-arbitration year in 2018 Rosario will need to keep his improved offensive output going to offset other diminishing skill sets. If Rosario can continue to build upon his improved plate discipline in 2018, he could finish the season as one of the more offensively productive outfielders in the American league.