Robbie Ray’s perplexing slider

If you’re a fan of (a) the Diamondbacks or (b) sabermetrics, you probably know who Robbie Ray is. His 2016 was truly bizarre — he paired an unsightly 4.90 ERA with a far superior 3.76 FIP, an elevated BABIP (.352) negating a high strikeout rate (28.1 percent). According to Baseball-Reference, he was worth 0.8 wins above replacement; by FanGraphs’s judgment, he was a three-win player.

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As is usually the case, Sam Miller’s take on the matter was by far the best:

Either Ray is still flushing the bad luck out of his system -- a reasonable, if uncertain, assumption -- or he has individual deficiencies that FanGraphs WAR doesn't pick up.

Ray appeared to deserve both his BABIP and his strikeout rate. On the one hand, his 89.4 mph average exit velocity against was the sixth-highest among 79 pitchers with 2,500 pitches. On the other hand, his 12.4 percent swinging-strike rate ranked 15th in that sample. His performance departed from the axiom that power pitchers allow weaker contact, allowing for the aforementioned WAR disparity.

This year? Things have gotten even weirder. Ray’s exit velocity has held steady at 89.8 mph; that places him seventh among 130 pitchers with 500 pitches. His whiff rate, meanwhile, has risen to 13.6 percent, good for 12th. In 2017, though, the gains are concentrated among one pitch in particular: his wipeout slider.

Last season, Ray’s slider fooled hitters pretty often (20.9 percent whiff rate) and garnered some relatively soft contact (87.3 mph exit velocity). This season, each of those has spiked — his slider has the second-highest whiff rate in baseball, at 27.4 percent, and the second-highest exit velocity in baseball, at 90.4 mph. That combination leads to this crazy graph:

Data via Baseball Savant

Nobody even comes close to Ray. His slider has that rare combination — it’s not hittable, but when you do hit it, it’ll travel pretty far.

Velocity may be partially to blame here. Everything in Ray’s arsenal is a little slower this year:

Image via Brooks Baseball

The slider has gone from 86.1 mph in 2016 to 84.8 mph in 2017; that means less gas to power past hitters. But that doesn’t explain how it’s become more deceptive. It’s not because of contrast with the fastball — his four-seamer’s velocity has dropped in turn from 95.3 mph to 94.1 mph.

Location seems to be the bigger problem. Ray’s slider has, in a way, moved in opposite directions this year:

Images via Brooks Baseball

He’s burying the slider more often this year: It’s gone below the Brooks-defined strike zone 65.9 percent of the time, up from 60.4 percent last year. But simultaneously, he’s thrown it middle-middle 6.7 percent of the time — that’s one out of every 15 sliders. A grooved breaking ball leads to stuff like this:

GIF via MLB.com

The slider has another factor working in its favor this year — Ray has used his curveball more often, which gives hitters two breaking balls to deal with. But when they’re able to make contact, they square it up, and he’s dealt with the consequences.

Whether it’s a matter of poor command or bad luck, Ray has had the same trouble this year as last. His hard contact has turned into long balls (18.4 percent HR/FB rate) instead of singles and doubles (.308 BABIP), but the issue remains that he’s allowed too much of it. For Ray to move from “enigma” to “legitimate ace,” he’ll need to improve his slider.

Ryan Romano is the co-managing editor for Beyond the Box Score. He also writes about the Orioles for Camden Depot, sometimes. Follow him on Twitter if you enjoy angry tweets about Maryland sports.