Cleveland Indians pitcher Corey Kluber is very different from the stretch

Corey Kluber carries himself like an old west Gunslinger on the mound, mowing his enemies down without a hint of emotion. He throws two plus-plus pitches, and when he's locked in his opponents are doomed. His unnamed breaking ball would have had him burned at the stake for sorcery 400 years ago.

http://www.fangraphs.com/blogs/what-is-corey-klubers-breaking-ball/

However, I've noticed that Kluber occasionally malfunctions during games. He can hum along for innings at a time without allowing a baserunner, but once one reaches things are more likely to fall apart. At the beginning of the year I called it a Klubot glitch that caused runs to duplicate themselves. Now, more than halfway through the year, I think there's more to it than that.

My explanation is that Corey Kluber is a much different pitcher when he throws from the windup compared to the stretch. The first is the ruthless Klubot that nearly threw a perfect game against the Cubs in 2014, and the other is just an above-average fully-human pitcher. I've passed this judgment only using the eye test, so in this article I'd like to take a look at the statistical differences between Kluber in both modes and compare them to the league average.

Admittedly, this isn't a perfect way to tease out the differences. When the bases are loaded, many pitchers return to the windup. Furthernore, the Tribe's Carlos Carrasco and others always throw from the stretch, and the type of base runner and where they are on the diamond also matter. I also checked the previous five years for the league, and the numbers for 2016 are really quite close to the same outside of the increased strikeout rate. Therefore, I've included just the league-wide statistics for the most relevant season: this one.

Kluber's career stats are included to give us an additional frame of reference about what is happening this season. Finally, it's easier to say "from the windup" and "from the stretch" than it is to say "with bases empty" and "with at least one man on base", but I am referring to them interchangeably. The goal here, whether it's a mechanical issue with the stretch or a change in strategy when a man is on base, is to figure out how different Kluber is, and how much wider that gap is than the league average.

All pitchers this season with bases empty

All pitchers this season with runners on base

Kluber this season with bases empty, followed by his career numbers

Kluber this season with runners on, followed by his career numbers

Now, the differences!

Charts on charts! It's a lot of data all at once, but here's what I've distilled it down to in the differences section: the first three rows show the difference in that statistical category between no men on base and runners on. Essentially, this is my approximation for the difference in performance in each category by pitching from the stretch vs. pitching from the windup. For example, the average pitcher throws 1.28 fewer strikeouts per nine innings from the stretch than they do from the wind-up. Meanwhile, Corey Kluber throws 2.96 fewer strikeouts.

Before we dig too greedily and too deep, here are my surface-level takeaways:

1. Corey Kluber is still an above-average pitcher whether pitching from the windup or the stretch.
2. This advantage is much more pronounced when Kluber pitches from the windup, because Kluber has a much larger performance drop than the league average pitcher in most of these metrics.
3. 2016 appears to underline an even more dramatic deviation from the league average pitcher for Kluber.

Now, let's take a look at some of the more interesting results we get out of this comparison. In 2016, the league average pitcher walks almost .3 more batters when pitching from the windup then from the stretch. Kluber walks .47 fewer batters this season. This isn't because he is striking more hitters out; as noted, he strikes hitters out much less often this season from the stretch. This drop in his strikeout performance is more than twice as large as the league average. When it comes to batting average, Kluber allows a whopping 70 extra points in 2016 from the stretch, while the league allows only 6 extra batting average points.

There are two more bad things that might be the most important pieces of the puzzle. This season Kluber allows .76 more dingers per nine from the stretch, and his BABIP rises by .047 points. Compare that to the league average of .25 fewer dingers per nine and a BABIP difference of five measly points. Interestingly, the leagues' difference in batting average may be explained by a slightly higher BABIP, but Kluber's higher average may not be.

Are Klubers numbers higher this season than we would expect based on his career? Yes, but he has consistently allowed many more home runs and hits from the windup. This is not just something that is happening in 2016. The numbers indicate that there really might be two different Corey Klubers. Fortunately, this is not one of them:

Drawing on my experience watching him pitch for the last few seasons, I offer this guess: when there are no baserunners, Kluber is a bit more aggressive, and willing to work more on the edges. He throws cutters that dart off of the plate and curves that break toward the other batters box in order to induce a bad swing. If the hitter takes, it's a ball, and if they take a cut, there's almost no way they're going to make contact. Once someone reaches base, the numbers seem to indicate that he throws more balls over the plate. It makes some intuitive sense; if Kluber is throwing more pitches that are easier to hit hard, that explains his consistently elevated BABIP from the stretch. That also explains why he would allow fewer walks while giving up more home runs.

It's also possible that his "stuff" is just much better from the windup. We know that pitchers tend to be a little bit less effective from the stretch, but I'm not inclined to think that this explains everything. The difference in Kluber's numbers indicate a completely different arm. If you set the side by side without context, no one would ever think they came from the same pitcher.

To prove one theory or the other, it would take quite a bit of time digging through PITCHf/x or Statcast to log the movement, velocity, and location of his pitches from the windup and the stretch. I'm not equipped to do so at the moment, and I'm also not very quick at logging and manipulating numbers. For now at least we can show that Kluber absolutely struggles from the stretch compared to the Klubot windup. The Indians would be well-served to try and find a way to bridge the performance gap between the Two Klubers.