Corey Kluber is Making History

Corey Kluber has been really good for a quite some time.

He’s a Cy Young Award winner and has finished in the top 10 in voting for three straight years. He trails only Clayton Kershaw and Chris Sale in wins above replacement since 2014, with 22.4 WAR.

Since returning from a back injury at the beginning of June, Kluber has struck out a ridiculous 40.7% percent of batters. He owns a sparking 36% K-BB%, 1.61 FIP and 40 ERA-. Since coming off the disabled list, Kluber has been Kenley Jansen — only Jansen as a starting pitcher.

The raw numbers since his return: 131 strikeouts in 86.1 innings against 52 hits and 15 walks.

Crazy good.

He struck out 11 Yankees on Friday to become only the fourth pitcher in baseball history to strike out at least eight batters in 12 consecutive starts, joining Randy Johnson, Nolan Ryan and Pedro Martinez. Not bad company. (Johnson did it four times, Martinez twice).

Here are the strikeouts from Kluber’s last outing agianst the Yankees pushing him into elite company:

What’s propelled Kluber, who was already great, to even thinner air?

He’s 31, so we don’t expect a leap in stuff. If anything, his velocity and movement should be in some state of decline. And his velocity has declined, though not dramatically — and gradually — from an average fastball velocity of 94.6 mph in 2014 to 93.1 this season.

His breaking ball’s average horizontal movement has also slightly declined. The wipeout pitch led baseball in horizontal movement in 2015 (9.99 inches) and 2016 (8.94 inches). It has slipped to 8.31 inches this season, which still ranks third in the sport, according to Baseball Prospectus’ PITCHf/x leaderboards.

Despite no increase in underlying stuff, since Kluber has returned from the disabled list at the beginning of June he has been on a remarkable run, the most dominant run of his career.

Kluber has made one easily identifiable change. He’s throwing his breaking ball more than ever this season, at a career-high rate for 24.2%. His breaking ball career average usage is 17.3% and his previous career high was 19.8% last season. Since coming off the DL, he’s thrown the breaking pitch 26.9% of the time.

Consider the following chart which shows a striking parallel increase between Kluber’s breaking ball usage and strikeout rate:

Kluber didn’t believe his stuff is playing any differently when I explored his strikeout surge in a feature for The Athletic last month.

“I’m not sure it’s as much me doing anything differently as much as it is guys just don’t care about striking out,” Kluber said. “Batters used to believe striking out was a bad thing. They changed their approach with two-strikes, shortened up.”

“I think it goes hand-in-hand,” said Kluber of his breaking ball usage and strikeout rate. … Guys a lot of times don’t really make adjustments. They go up there swinging for the fences. More times more than not [the breaking ball] is the best pitch to take advantage of that.”

While his breaking ball is still elite but moving at a slightly less rate, he is enjoying a career best whiff rate per pitch on his breaking ball (52.5%) and swing rate. His whiff rate leads baseball.

If batters are not going to adjust, Kluber is willing to hunt for strikeouts more and more, and for swing and miss. Makes sense, right?

Against the Yankees, Kluber got eight of his 11 strikeouts on breaking balls. Against the Blue Jays on July 23, 12 of his 14 strikeouts were against the breaking ball.

We’ve seen much written at FanGraphs and elsewhere about batters being more accepting of taking on more strikeouts as a byproduct of an increased focus on creating power. And Kluber has taken advantage of this approach to a historic degree to reach this new level of excellence.

While Kluber’s velocity is not increasing, while his breaking ball is not moving more often, it’s not just that he’s changed pitch usage it’s that he’s better locating the breaking ball and getting ahead in more counts to make batters more susceptible to his breaking stuff in two-strike counts. Kluber is also enjoying a career best first-pitch strike and zone rates.

Consider his slider locations against lefties since June 1 this season.

And his slider location against righties since June 1 this season:

Then consider his slider location against lefties from the beginning of the 2014 season to May 30 this season:

And the consider the same time period against righties:

His already excellent command seems to be sharpening further.

And while Kluber is adjusting with pitch usage and location, batters are not. It’s allowed for a historic strikeout surge, which is even eye-opening in this age of strikeouts. In a game becoming more extreme in regard to hunting power, Kluber is using that aggressiveness to his advantage.