The Evolution of Twins Left Fielder Eddie Rosario

Minnesota Twins’ Eddie Rosario swings for a grand slam against Arizona Diamondbacks pitcher Braden Shipley in the first inning of a baseball game, Sunday, Aug. 20, 2017, in Minneapolis. (AP Photo/Jim Mone)


On the surface, it’s easy to see that this isn’t the Eddie Rosario of previous seasons. The 25-year-old Twins left fielder has already set career-high marks in walks and home runs, and he’s hitting .295/.337/.502 on the season. That’s a .840 OPS for a hitter who came into the season a career .268/.292/.443 hitter — a 105-point OPS increase.

In fact, Rosario set a career-high in walks with his 16th walk of the season back on July 6 against Baltimore as well as his 14th home run back on Aug 8 against Milwaukee — a two-homer game. He’s at 28 walks heading into Friday’s action, with a chance to not only double his previous career high of 15, but maybe an outside shot to triple it.

The changes weren’t immediately evident and perhaps weren’t applied right out of the gate. Heading into the month of June, Rosario was hitting .269/.302/.431 — or in other words two points off his career OPS and pretty much in line with who he’s been as an MLB hitter to this point.

Rosario has never been short on talent and physical tools. Baseball Prospectus twice ranked him in their top-100 prospects, and his minor league numbers (.294/.340/.484) reflect an accomplished hitter even while the team yo-yo’d him between the outfield and an ill-fated second base attempt.

In the big leagues, it became clear that Rosario’s mentality was to swing first and ask questions much, much later. When he made contact, the ball soared, and he could spray it to all fields. However, the contact was infrequent, the walks were nonexistent and the overall approach was flawed, to say the least.

But when researching him prior to the season, I made an interesting discovery. According to Baseball Reference, Rosario had an OPS of .900 to each field. That is to say, when he hit to left-center-right field individually, he absolutely throttled the ball. Thus, it would seem that he just needed a bit better plate discipline to unlock his true talent.

It’s hard to see that tree in a crowded forest. Not many players can get out of their own habits at the plate, and even Rosario didn’t really get that message right away even this season, either.

Take a look at his walk rate, month-by-month and then half-by-half:

  • April – 3.5 percent

  • May – 5.8 percent

  • June – 7.1 percent

  • July – 7.6 percent

  • August – 7.3 percent

  • First Half – 5.4 percent

  • Second Half – 8.0 percent

For a reference point, the American League average this season is 8.5 percent. Rosario’s season mark is 6.3 percent. While that still won’t make anyone forget about Joe Mauer or even Miguel Sano, it represents nearly a twofold increase from his previous career-high mark of 3.4 percent.

Not surprisingly, it also shows up in Rosario’s discipline stats, which can be found at Fangraphs. In his rookie season, Rosario chased an absurd 45.6 percent of pitches outside of the zone. He improved slightly last season (41.7 percent) and is now all the way down to 36 percent this season. Again, that won’t make anyone forget about what Mauer is doing, but it’s trending to the point where the AL average (29.8 percent) is in the crosshairs, potentially.

As one can see from the attached charts courtesy of Brooks Baseball, Rosario can still be exploited middle-in and at times up-and-in, but across the board, he’s improved a fair amount at the pitches he’ll chase out of the zone. The most obvious improvement is on pitches away, where he’s sliced his chase rate by a large margin.

Along with the improvement in games, Rosario has also been working with hitting coach James Rowson and assistant Rudy Hernandez on his hitting approach. I caught up with Rowson a while back to chat about that exact thing, which you can hear here:

Is Rosario out of the weeds as a hitter? Not necessarily. But it’s not without precedent that a young, talented hitter with questionable plate judgment blossoms into a star. Heading into his age-25 season, Kirby Puckett’s career walk rate was just 2.7 percent. By the end of his career, it was 5.7 percent. Is Rosario the next Puckett? We won’t claim that. We just can’t write it off either, however.

By: Brandon Warne