Eddie Rosario isn’t especially awesome at anything on a baseball field. That being said, he’s been an above-average producer on offense in each of the last few seasons, especially in the power department. While he’s posted better than league average wOBA in four-straight seasons, his xWOBA has been lower in three, and below league average in two of those. As a Statcast denier, it seems as though Eddie Rosario could be in the throes of a quite serious case of Kris Bryant Syndrome.
As a merely average ball-batter, but past superstar producer, it’s no wonder Kris Bryant’s had such a serious baseball-related disease named after him. Far more serious than Groat’s Disease, Kris Bryant Syndrome (KBS) occurs when a player consistently out-produces his batted-ball data in the counting stats department. In every season of his career, Bryant has out wOBA-ed his xWOBA, while the league as a whole, actually out-xwOBAs their wOBA. On average, Bryant’s been a better hitter than Rosario, but his consistent split between actual and expected outcomes denies the probability that randomness is at fault. To date, it’s unknown if the cause of the affliction has genetic roots, or if environmental factors are entirely to blame.
In Rosario’s case, it’s hard to see where his production is coming from. He doesn’t hit the ball hard (28th percentile exit velocity) or often (18th percentile hard hit percentage), and he doesn’t walk frequently (38th percentile walk percentage). While he had an above average expected slugging (57th percentile), the only thing on offense he does at an elite rate is make contact, as his 14.7 percent strikeout percentage finished in MLB’s 89th percentile. So how the heck did he finish with an OPS 52 points higher than league average, and a wOBA 13 points higher than league average?
While I’d like to imagine a more cosmic commonality between Bryant and Rosario, Occam’s Razor suggests the culprit for each of their overperformance is their consistently elevated launch angles. Bryant, the titular basis for the Syndrome itself, has a career mark almost double the league average, but Rosario’s launch angle is right in between league average and Bryant’s at 15.4 percent. In 2020, that number crept up to 18.1 percent, as did the positive disparity between his wOBA and xwOBA.
Specifically, though their average launch angle belies exactly what’s going on, their elevated launch angle aids each of them. This FanGraphs article by Alex Chamberlain explains how although BABIP and xwOBAcon are each at their most valuable with a launch angle around 13 degrees, xwOBAcon, which includes home runs, has a second peak value around 25 degrees. While each player’s xwOBAs are dragged down by few line drives around that first peak, they benefit from hitting a few balls right around that optimal launch angle for a home run that might even get caught were there no fences. In 2020, Eddie Rosario hit nearly twice as many homers (13) as he did doubles (7), optimizing his swing for that second xwOBAcon peak at 25 degrees, at the expense of that first peak.
Rosario’s overall xwOBA and xwOBAcon are still both below league average, but hitting a bunch of wall-scrapers deflates his expected stats while putting up solid counting ones. In 2020, Rosario hit 1.8 more homers than his xHR total, and had the 25th-lowest no doubter percentage in the MLB. In 2019, Kris Bryant’s most recent passable full season performance and the first year of expected homers’ existence, he had the 13th greatest positive discrepancy between his actual and expected homers. While these two could be capable of consistently producing a swing built to deliver wall-plus-one-foot homers, their production ceiling isn’t particularly high due to their lack of raw power.
The shift Rosario’s made over the course of his career — hitting more and more balls in the air — hasn’t really made him better or worse, it’s just made his production spottier. His homers have kept his production afloat, but those boons are fewer and farther between.
On defense, Rosario’s been bad from the get go, finishing as a below average defender in each of his full big-league seasons per OAA. In 2020, Rosario was the game’s 90th worst defender amongst 244 qualified candidates. Rosario’s offense remains bit of a question mark, but his defensive production is confirmed to be non-existent.
The Yankees have an overflowing outfield, assuming Gardner re-ups, Tauchman isn’t dealt and Judge stays healthy. In addition to retaining Frazier and Hicks, there’s not really room for Rosario — even if he’d likely benefit from Yankee Stadium’s short right-field porch. If the Yankees were to lose another outfielder or designated hitter (looking at you Giancarlo) to injury, Rosario is someone who could passably plug the hole in a trade or late-signing. However, he’s not someone who the Yankees, as currently constructed, ought to aggressively pursue this offseason.