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Craig Kimbrel is the latest high fastball revolutionary

The Red Sox are getting the elite closer they traded for last year, thanks to one strategic change he’s made.

Tampa Bay Rays v Boston Red Sox

When Boston traded Manuel Margot, Javier Guerra, Carlos Asuaje, and Logan Allen to the Padres for Craig Kimbrel, the consensus was that the Red Sox paid a hefty price, one that could only be justified if the closer returned to something like his 2012 form. That didn’t happen in 2016; Kimbrel’s strikeout rate stayed in the high-30s, rather than the high-40s, and his walk rate of 13.6 percent was the highest of any full season in his career. Kimbrel was still very good, but his FIP of 2.92 and WAR of 1.2 were not what Boston had paid for.

But if 2016 made the trade look ill-advised, the first month and a half of 2017 have made it look brilliant. After his multi-inning save on Thursday in Milwaukee, which included an “immaculate” ninth inning (three strikeouts on nine pitches), Kimbrel is sitting on a 55.4 percent strikeout rate, a 3.6 percent walk rate, a 0.47 FIP, and a WAR of 1.1. He ranks 14th in the league in WAR among pitchers, despite being a reliever. In his 15 23 innings, Kimbrel has been worth roughly as much as Clayton Kershaw and Max Scherzer, each of whom have thrown about three times as many innings.

Those are numbers that we rarely see from any pitcher, and they’re a glimpse of the pitcher the Red Sox hoped they were acquiring the rights to. Nor are his numbers just a trick of the early season sample sizes, and the volatility of single-inning relievers. We can use FanGraphs’ neat graphs tool and look at Kimbrel’s strikeout percentage over periods of 15 games, the same length as his 2017 to date. Even in short stretches, the righty closer has rarely been as good as he has been recently:

The only other 15-game stretches in which Kimbrel has struck out batters at a rate over 50 percent, and walked batters at a rate below 5 percent, came during his otherworldly 2012 season. Kimbrel ended that year with a 50.2 percent strikeout rate, a 6.1 percent walk rate, a FIP of 0.78, and a WAR of 3.3 in only 63 innings. Since that season, however, Kimbrel’s strikeout rates had generally trended downward, while his walk rates ticked upward, and his seasonal value fell correspondingly. Especially after 2016, a return to that form seemed exceptionally unlikely; yet here we are. What happened? What changed for Kimbrel after 2012, and what changed before 2017?

It’s helpful to first eliminate some of the possible explanations that don’t fit this situation. With pitchers, especially high-octane closers like Kimbrel, velocity is often the first place to look for evidence of a decline or resurgence. But Kimbrel’s fastball velocity has remained entirely steady over the course of his career, with no peak in 2012, no decline from 2013–16, and no spike in 2017.

Nor has there been much of a change in Kimbrel’s two-pitch repertoire, or in how he uses those pitches. He hasn’t added a pitch, and both his curveball and fastball look exactly the same as they always have, in terms of their horizontal and vertical break. In other words, the raw materials Kimbrel is working with — the types of pitches at his disposal, and the velocity and movement of those pitches — are almost wholly unchanged. If there’s an explanation other than randomness for his dominance over the last six weeks, it will lie in Kimbrel’s approach, and the way that he’s using those unchanged raw materials.

He hasn’t made a dramatic change in the rate at which he throws his two pitches. Kimbrel might be using his fastball slightly less than he has in the past, in favor of increased curveball usage, but it’s a very slight difference. Kimbrel’s highest yearly fastball rate of 72.9 percent is fairly similar to his current rate of 63.9 percent.

The only real difference in Kimbrel’s approach from 2013–16 to 2017 is in where he’s placing his fastball. In 2017, he seems to be making a more conscious effort to locate it at the top of the zone, and forsaking the bottom almost completely.

This is a move that a number of pitchers have made in recent years, and it’s been particularly effective for players who, like Kimbrel, feature fastballs with high spin rates. Those are the fastballs that have the largest “rising” effect, as they resist the downward pull of gravity on their path to the plate. Batters pull the trigger on a swing, expecting the pitch to be in the zone, but as the fastball falls less than expected, it generates a whiff or a pop up instead of solid contact. That might not be how it always works, but it’s how its supposed to work, and it’s how the strategy is working for Kimbrel this year: the whiff rate on his fastball is higher than it’s ever been.

This is the kind of simple change that can revolutionize a pitcher’s entire season. With more whiffs, Kimbrel is going into deep counts less often, and walking less batters. He’s allowing fewer balls in play, and relying less on his fielders or the kindness of outfield dimensions to be successful. Doubling the rate at which opponents swing and miss at your fastball is a great way to ensure success.

Craig Kimbrel was still Craig Kimbrel last year, and he’s still Craig Kimbrel this year. But there’s a difference between Craig Kimbrel and ~ Craig Kimbrel ~. Thus far in 2017, he’s looking more like the latter, the Craig Kimbrel who strikes fear into the hearts of opposing fanbases, mows through lineups like a thresher through wheat, and is possibly the best reliever in all of baseball. Kimbrel has always had the raw talent needed; this recent surge has been all about a new strategy. Strategies can be countered, of course, so only time will tell if the rest of the league can adjust to Kimbrel’s new approach. But until and unless they do, don’t expect many last-minute comebacks against the Red Sox.

Henry Druschel is a Managing Editor at Beyond the Box Score. You can find him on Twitter at @henrydruschel.