Yandy Díaz and the Groundball Revolution
If you’ve followed FanGraphs the past few years, you know the Yandy Díaz story by now. As an Indians prospect, his contact and on-base abilities marked him as a potential major league contributor, but his physique hinted at more: Díaz excelled despite a plethora of groundballs, and he also had elite bat speed and exit velocity numbers at times. If he could just aim up a little more, the thinking went, he could be the next launch angle success story.
When the Rays acquired him in a trade before the 2019 season, it wasn’t hard to connect the dots. The Rays acquired an already-usable player with a fixable flaw? We’ve certainly heard that story before. Indeed, Díaz spent 2019 putting balls in the air at a rate he’d never approached before. His fly ball rate spiked, his groundball rate dropped, and he hit double-digit homers for the first time in his professional career.
All of those balls in the air made Díaz a different hitter, but they didn’t change the core of his approach at the plate: wait patiently for a pitch he liked, then try to hit the snot out of it. As FanGraphs alum Sung Min Kim detailed, he mostly accomplished it without a swing change; he simply focused on finding pitches to drive rather than spraying grounders.
The evidence was there if you wanted to look for it. His air pull rate, the percentage of line drives, pop ups, and fly balls that he sent to left field, jumped significantly. At the same time, he started hitting fewer grounders; his GB/FB ratio dipped to heretofore unseen lows:
| Year | GB/FB | Air Pull% |
|---|---|---|
| 2017 | 3.13 | 9.8% |
| 2018 | 2.29 | 9.5% |
| 2019 | 1.59 | 18.9% |
