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Sonny Gray’s Slider has Made Him an Ace

Coming into the year I was cool on Sonny Gray at the draft table because of what I believed to be an inflated cost against what we had seen from him to that point. He was being priced as a top 20 starter and I thought he needed to actually improve upon his 2014, not just repeat it, to justify such a price tag. How's top 3? Is that good? Does that work? Gray has pitched at an ace level through the first 14 starts of the season by recapturing most of the strikeout rate we saw in 64 innings back in 2013.

Gray had a 26% rate in 10 starts and two relief appearances with the A's that year and the results were just as good with a 2.67 ERA and 1.11 WHIP. Last year he showed he can hold up over a full season with 219 innings and his 3.08 ERA and 1.19 WHIP were great, but a 20% strikeout rate kept him from the upper echelon of starters and made him more of a fantasy #2. That felt right. With his premium groundball rate (56%), he can afford to be a little lower on the strikeouts and still post tremendous results.

I saw something like a 3.30 ERA season for 2015 and he's gone ahead and more than halved that at 1.60 through 95.7 innings with a 0.93 WHIP. His strikeout rate has jumped up to 24% with little cost to the groundball rate at 54%. The 24% composite rate might actually undersell what he's been doing for the bulk of the season. He started out basically how I expected he might with three strong starts results-wise (2.11 ERA, 0.99 WHIP), but just a 15% strikeout rate. He didn't fan more than five in any of those outings.

Since then he has fanned fewer than six just three times in 11 starts, posting a 27% strikeout rate in the 74.3 innings of work. The run includes four 9+ strikeout games with a season-high of 10 at Texas on May 3rd. The slider was responsible for seven of those 10 strikeouts and it's been a driving force behind not only the strikeout surge, but his excellent overall success, too. The two are obviously related as more strikeouts often bring more success, but this is whole new level for Gray.

Maybe we should've seen this coming. Or maybe those who were valuing him as a top 20 starter did and I simply missed the boat. Gray's slider was a force last year, but the usage wasn't there which muted the impact. His slider allowed a .342 OPS and 37% strikeout rate last year, but it was used just 11% of the time so it only accounted for 81 PA. It has already eclipsed that figure by 27 this year thanks to a 19% usage.

The slider is allowing the exact same .342 OPS this year in those 108 PA with a 48% strikeout rate. Neither righties nor lefties have stood a chance against it. Righties have a .138/.194/.138 line with a 42% strikeout rate in 62 PA and lefties are at .089/.109/.244 with a 57% strikeout rate in 46 PA. Gray's slider has a 29% swinging strike rate, baseball's best mark among the 35 pitches who have thrown at least 250 sliders (Gray has thrown 257). Even if you drop the threshold to 150 pitches which brings in some relievers, he's still only second to Blake Treinen (31%).

Highlighting the excellence of the slider might overshadow the rest of his arsenal. By pitch values at Fangraphs, only his changeup is generating a negative value and barely so at -0.7. The fastball (7th), slider (5th), and curveball (4th) are all top seven or better by pitch values among qualified starters. The curveball used to be the go-to out pitch. He has cut the usage substantially, from 27% to 14%, but it remains a groundball weapon that the opposition can't handle. It's allowing a .111/.111/.111 line with an 18% strikeout rate in 45 PA, but also a 62% groundball rate.

He uses a four- and two-seamer and the two have combined to allow just a .623 OPS which is 11th-best among the 45 arms with at least 800 fastballs thrown. His 13% strikeout rate is below average, but a 56% groundball rate (fourth-highest) mitigates the need for strikeouts off of his heat. A forgotten element to Gray's game is the fact that he throws in the mid-90s with his fastballs. In fact, he's at a career-high 94.9 MPH with the four-seamer (94.5, 94.4 in his first two seasons) and at 94.3 MPH with the two-seamer (94.1 and 94 even the first two seasons).

Gray is an ace. He is pitching like an ace, but a lot of major leaguers can do that for a run. Gray has displayed the skills and stuff to back it up. Anyone with a 1.60 ERA is pitching over their head on some level, but he's also earning a lot of his own breaks with tremendous pitching. If you are aiming to sell high, make sure you're getting a top 20-type of hitter at worst.