As with most rebuilding teams, the San Diego Padres aren’t in any particular need of a strong bullpen, and they’ve handled this season’s trade deadline accordingly. As of July 30, they’ve already traded away Ryan Buchter and first-half closer Brandon Maurer, and relief ace Brad Hand is expected to follow this offseason. The rest of San Diego’s bullpen is, for the most part, unexceptional; not including Hand, the most-used relievers still on the team are Craig Stammen and Jose Torres, neither of whom have a positive WAR or a FIP under 4.50.
It’s fortunate for San Diego, then, that Kirby Yates has quickly become their most reliable non-Hand option in relief. The team plucked Yates, a relatively unknown 30-year-old Hawaiian right-hander, from the waiver wire in late April, prior to which he’d spent time as a Ray, a Yankee, and, for one inning in 2017, an Angel. Minus a disastrous 2015 season, due in part to a HR/FB ratio of over thirty percent, both Yates’s FIP and xFIP have consistently been below 4.00. He’s also demonstrated an impressive strikeout ability over the past few years; his K rates in ’14 and ’16 were both approximately 27%, and in 2015, his worst season, he still managed to strike out nearly 23% of batters faced.
Since his move down the California coast in April, though, Yates has emerged into the Padres reliever perhaps most likely to take over the closer role – assuming Hand is dealt as expected – and has been one of the more unexpectedly impressive relievers of 2017. In prior years, Yates’s terrific strikeout rate was often coupled with a walk rate that was passable at best (7.6% in 2015) and dreadful at worst (10.3% last season). This season has seen progress in both areas – his BB% is down to 6.3%, and he’s struck out over 38% of the batters he’s faced. Yates’s improvements in strikeout and walk percentage have been sufficient to land him among the league leaders in both K%, where he ranks seventh among qualified relievers, and K-BB%, where he ranks fifth, at 31.9%. For reference, Andrew Miller ranks sixth at 31.0%, and other members of the top five are comprised of arguably the best relievers in the game, including Craig Kimbrel and Kenley Jansen.
Of course, it’s a bit premature to tout Yates as a Kimbrel-quality option out of the Padres’ bullpen. He doesn’t have the same electric stuff, or anything near the track record, of his peers on the league leaderboards, and he’s been the beneficiary of a strand rate of almost 91%. At 3.09 and 3.01, his FIP and xFIP, respectively, are also significantly higher than his 2.23 ERA, so there’s a fair bit of evidence to suggest that Yates isn’t as good as his basic stats indicate. With that being said, though, there’s a lot to like about Yates’s performance this year. There’s nothing fluky about a 38% strikeout rate, and his SIERA score, at 2.24, has been far more bullish on Yates than have his FIP and xFIP. So while Yates isn’t necessarily becoming the next great San Diego closer, his improvements this year are far too drastic to be chalked up entirely to luck.
Instead, I believe there are a couple interrelated reasons for Yates’s recent success. In June, Jeff Sullivan wrote about Brewers starter Chase Anderson‘s 2017 breakout, noting that Anderson had started shifting his location on the rubber. Against right-handed hitters, Anderson began his wind-up from the far right side of the rubber; this was, as Sullivan explained, about “playing the angles,” adding that Anderson could get his pitches “sweeping away” from these batters.
Yates, it appears, has followed the same line of thinking. Compare the starting point of Yates’s delivery between the past two seasons:
We can also see how much his pitches’ respective routes to home, as illustrated by PITCHf/x, have changed since last season:
Compared with a .283/.372/.457 slash line in 2016, righties are hitting just .171/.227/.305 against him this year, with a .227 wOBA and .224 xwOBA. With Yates’s new starting point on the rubber, his pitches have been able to more effectively “sweep away” from right-handed batters, since they start significantly farther to the right, and he’s seen excellent results against righties in particular. This effect, I believe, has been a significant contributor to Yates’s success. As the above graph indicates, his fastball and slider travel most towards the outer section of the plate, which may be giving right-handed hitters more difficulty in the batter’s box.
However, that’s not the only interesting development regarding Yates’s slider. According to PITCHf/x, he’s throwing roughly four percent more sliders against right-handers, and his fastball usage has declined by roughly the same amount. His slider hasn’t spun the same this year as it has in the past, either: according to PITCHf/x, the pitch’s spin rate has risen from 594 to 1,962 RPM this season. (I should note that BaseballSavant sees a negligible difference in the average spin rate of Yates’s slider, so there may be an error in the data.) Regardless, it’s hard to deny that the pitch’s movement has changed:
As evidenced by the wide spread in 2017, Yates’s slider still seems like a work in progress, but it’s clear that the pitch has taken on some new movement. FanGraphs, through PITCHf/x, scores his slider’s xMov as having shifted from 1.4 to -2.2, indicating that the pitch has actually begun moving towards right-handed batters. This doesn’t invalidate the merits of Yates’s shift on the mound, though – the new angle might still be affecting how righties pick up his pitches, and the majority of his sliders do tend towards the outer half of the plate, thus still “sweeping away” from the batters.
Yates briefly spoke on his slider in a May interview with Jeff Sanders of the San Diego Union Tribune, saying the pitch was “getting back to where it used to be.” I found this a curious phrase for Yates to use, seeing as how the pitch has done anything but revert back to its old movement. His next sentence, however, may answer this question. Yates says he’s “incorporated a splitter that [he] feels pretty confident in,” and later mentions that over the offseason, he developed a the pitch as a sort of contingency plan against an occasionally less-than-trustworthy slider.
I’m not very familiar with the inner workings of PITCHf/x, but it seems possible that the system could be classifying some of Yates’s new splitters as sliders. Not only would this account for the change in his slider’s horizontal movement, but it’d also explain Yates’s description of the pitch. Overall, though, I believe Yates’s newfound success can largely be attributed to the above adjustments he made over the offseason. He may not become the next Trevor Hoffman, but Yates has shown the Padres more than enough to feel a bit more comfortable with their bullpen, even after Brad Hand is dealt this winter.