Edwin Díaz Has Been Nearly Unhittable
This is Jake Mailhot’s first post as part of his May Residency at FanGraphs. A lifelong Mariners fan, Jake now lives in Bellingham, Washington, just a little too far away from Seattle to make it to games regularly, which is sometimes for the best. He is a staff editor at Mariners blog Lookout Landing. He can be found on Twitter at @jakemailhot.
There has been no shortage of remarkable relief performances during the first month of the season. Jordan Hicks and Tayron Guerrero are playing a game of one-upmanship with their fastballs. Josh Hader is striking out basically everyone he faces. Adam Ottavino resurrected his career in an abandoned storefront. But the most impressive performance of all might be what Edwin Díaz accomplished in April.
The ninth batter Díaz faced this season was also the first to actually put the ball in play — he’d struck out the first eight. Seven appearances into the year, he finally gave up his first hit, a single to Jed Lowrie. He gave up just one other hit the entire month. Among pitchers who’ve thrown 10 or more innings, possesses the fourth-highest swinging-strike rate and has produced the lowest overall contact rate when batters actually swing. If you prefer more traditional accolades, he’s also leading the majors in saves. His performance earned him the April AL Reliever of the Month Award. Any way you slice it, Díaz has been pretty great so far.
Díaz has shown flashes of dominance like this before — his 2016 rookie campaign was good for 1.9 WAR on the back of a 2.04 FIP — but he’s always been a little too erratic for his own good. Some of his success in April came despite the inherent chaos of slinging a projectile at 98 mph. He’s already walked nine batters and hit three more, and he’s given up a pair of home runs in May already. A quick look at his plate-discipline stats reveals that Díaz is throwing in the strike zone at the lowest rate of his career, around six and a half points lower than last season. And he isn’t really inducing any more swings on those pitches out of the zone — in fact, batters are swinging far less often at his pitches overall. But again, when batters do swing, they just cannot make consistent contact. Díaz’s contact rate of 55.2% is better than Aroldis Chapman’s, Josh Hader’s, and everyone else’s.
So what has made Díaz so effective this year when he does find the zone?