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The curious case of Craig Kimbrel

Typically considered the best closer in baseball, the Padres' Craig Kimbrel is struggling in 2015. Examine why he's become more hittable and homer-prone, despite generating more swings and misses than ever.

What is the source of Craig Kimbrel's 2015 struggles?
What is the source of Craig Kimbrel's 2015 struggles?
Kirby Lee-USA TODAY Sports

Padres' closer Craig Kimbrel has had a rough start to the 2015 season. After being sent to San Diego in a blockbuster trade in April, Kimbrel has actually performed at a lower level despite moving to Petco Park. Through June 8, Kimbrel has a 4.29 ERA, 3.30 FIP, 2.64 xFIP, and a 5.51 rating by Baseball Prospectus' DRA through 21.0 IP. It suffices to say, these are all career-worst numbers for the four-time All-Star closer. And he's earning these figures in one of the most pitcher-friendly ballpark in the majors.

Looking at his peripherals, Kimbrel is still striking out and walking batters at fairly typical rates - 34.1 percent and 9.9 percent, respectively. However, a .375 BABIP and three home runs allowed are atypical for him (four home runs is his single-season high).

Craig Kimbrel appears to be more hittable this season, and his batted ball profile is reflecting it. Of all batted balls hit against him this season, 29.4 percent have been line drives, the worst rate of his career. Additionally, to this point Kimbrel has only generated 35.3 percent ground balls, another career-worst.

Line drive rate and BABIP are in many instances less reliable than other metrics - depending on the case, there may reason to believe these deviations are luck-influenced. For instance, 21.0 IP is still a fairly small sample size, FanGraphs reveals that batters have made lower than normal hard-hit contact against him in 2015, his 17.7 percent swinging strike rate is a career-best, and some of the worst damage against him was in Coors Field.

However, there may be some evidence that Kimbrel has performed at a lower level in 2015. Throwing 62.2 percent strikes is below his 65.2 percent average from 2010-2014. Potentially as a result, he has only a 26.7 percent O-Swing rate this season (typically, batters swing at 31.9 percent of pitches he throws outside the strike zone). Batters are also swinging more often at the pitches they should be swinging at (those in the zone; he has a 69.7 percent Z-Swing, the highest rate of his career).

2010-2014 2015
Four-seam 0.176 0.258 0.083 0.264 0.300 0.550 0.250 0.395
Curve 0.110 0.121 0.011 0.291 0.143 0.143 0.000 0.333

Craig Kimbrel throws a four-seam fastball, and a power curveball. This season, the curve has maintained its effectiveness, and the Pitch F/X data on Brooks Baseball related to velocity and movement reinforce this. However, his typically deadly four-seam fastball is getting beaten hard.

Year Velocity Horizontal Vertical
2010 96.30 -5.94 8.22
2011 96.89 -5.97 8.04
2012 97.81 -6.21 8.39
2013 97.85 -5.78 8.28
2014 98.05 -6.03 8.98
2015 98.69 -5.65 9.62

Along with the curveball, Kimbrel's four-seam fastball is actually averaging the highest velocity of his career. More worrisome would be the lower magnitude of horizontal movement (a career-low, if just barely), and his highest magnitude of vertical movement on record. Those factors indicate a harder-thrown, flatter pitch. Another potential problem is where he is throwing the fastball.

Craig Kimbrel Four-Seam Fastabll

In the above GIF, the zone on the left is Kimbrel's four-seam fastball from 2010-2014, and on the right is during the 2015 season. Both sides transition from the percentage of time the ball is thrown in a given zone, to slugging percentage allowed in that zone. As can be seen, Kimbrel typically throws the pitch all over the zone, with a bit of a focus towards high and arm-side.

In 2015 however, he has left the four-seamer in the dead-center of the zone a higher percentage of the time than any other. Predictably, hitters have crushed those pitches to the tune of a 1.556 slugging percentage, and a staggering 1.000 ISO against.

It appears that Craig Kimbrel is currently suffering from a fairly common problem for pitchers - leaving a flatter fastball over the middle of the plate. Major leaguers hit those kinds of pitches regardless of how hard it is being thrown.

Returned control would be a significant improvement - Kimbrel regularly challenged hitters with fastballs and had success in the past. Fortunately for the Padres, their closers' fastball movement has also slowly moved back towards prior career rates over the last two months, although the effectiveness has yet to be seen. Time will tell if he regains his prior form.

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Spencer Bingol is a Contributor at Beyond the Box Score. You can follow him on Twitter at @SpencerBingol.