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Kirby Yates has been one of the best relievers in baseball

After bouncing around for three years, Yates seems to have found a home in San Diego, but he will probably be headed elsewhere soon.

MLB: Chicago Cubs at San Diego Padres Jake Roth-USA TODAY Sports

Kirby Yates is not a household name, so you’re forgiven if you did not know he existed. Playing for the San Diego Padres does not help either. But somehow, playing for one of the worst teams in baseball, in one of the best cities to live in weather-wise, Yates is put together a quiet but an effective year. In fact, his numbers suggest he could soon be shipped to a contender at the trade deadline later this month, and bring the Padres a legitimate package in return.

On the surface, his ERA of 2.48 ranks 39th among relief pitchers in all of baseball — made worse by the two-run, one-inning outing Yates made for the Angels before being DFA’d. Since being picked up by the Padres off waivers, he’s pitched in 28 innings with a stellar 1.93 ERA, 2.40 FIP and 13.34 strikeouts per nine innings. Among pitchers leaguewide with at least 20 innings pitched, he ranks 14th in strikeout rate and 26th in strikeout-to-walk ratio. He combines the strikeouts with a marginally high home run rate of 1.55 per nine innings, relatively high walk rate of 6.8 percent, and an extremely high fly ball rate of 53.5 percent (the league-average fly ball rate for relief pitchers is 36.1 percent thus far in 2017).

So what has made Kirby Yates so successful? For starters, he’s generating a high whiff rate of 18.1 percent — good for sixth in MLB behind Craig Kimbrel, Roberto Osuna, Chris Devenski, James Hoyt, and Kenley Jansen — and a in-zone contact rate of just 71.8 percent, fifth in MLB. Here’s a look at how his pitch mix has changed over the past 4 years:

Pitch Mix

Year Fourseam Curve Slider Change
Year Fourseam Curve Slider Change
2014 53.62% 3.10% 38.40% 4.87%
2015 56.13% 16.91% 18.38% 8.58%
2016 59.92% 4.77% 32.29% 3.02%
2017 62.14% 0.00% 28.51% 9.13%
pitch mix data: brooks baseball

Over the years, Yates has increased his usage of his fastball and changeup, which seems to be paying dividends. His slider has varied over the years from 38 percent to 18 percent, but remains an important part of his arsenal.

Let’s look at his whiff rate on these pitches over the years:

whiff rate

Year Fourseam Change Slider
Year Fourseam Change Slider
2014 7.16% 21.21% 13.46%
2015 10.92% 17.14% 8.00%
2016 11.74% 29.17% 12.06%
2017 19.71% 24.395 17.97%
data: brooks baseball

Yates is generating most of his whiffs on fastball and changeups (the same pitches that he’s been using more often), although his slider isn’t too far behind.

It looks like Yates’s improvements have been the result of him identifying what he’s good at, and doing that more. Look at his zone profile through last year:

and from this year:

Yates has done a better job of keeping the ball down in the zone, where his whiff rate has significantly improved. In fact, his command of the entire strike zone has improved significantly.

Above average velocity, along with slight arm side run (-7.52 horizontal movement on his fastball and -5.86 on his change up, according to Brooks Baseball) has helped Yates generate a high amount of swings and misses as well as a relatively high fly ball rate. In that sense, his success on fastball/change up combo is somewhat reminiscent of Marco Estrada of 2015 and 2016, although Estrada generated his whiffs in a different manner.

The important question will of course be: do contending teams think that the changes Yates has made this year sustainable? Having a high fly ball rate at Petco Park is not the same as having a high fly ball rate in any of the many smaller ballparks. Will teams be willing to bet that he could be a useful piece to their playoff run down the stretch? Yates, and the Padres, will hope that at least one of them will be.