Analyzing Craig Kimbrel's Rising Fastball

The other day, I came across a Pitcher List article by Michael Augustine that talked about Bauer Units and how the concept can have real world application with samples of MLB pitchers.

First, a quick review of Bauer Units. BU = spin rate (RPM) / velocity (MPH)

This normalizes the effect of spin on a fastball relative to velocity for comparison among pitchers. The league average Bauer Units is 24. The higher the Bauer Units, the more "hop" or "rise" is perceived on a fastball, and the lower the Bauer Units, the more "sink" on a fastball.

One of the players in Augustine's sample of pitchers with average Bauer Units was the Yankees' Luis Severino, who notched an average of 24.31 BUs on his 4-seam FB through August of 2018. The article went on to explain how, essentially, Severino had more success living lower in the zone but that it didn't mean much considering his OBA on FBs alone (.273) was not very impressive. What could have contributed to this is that for "every 1.54 pitches [in the zone], he throws one [out of the zone]" and hitters are sitting on those fastballs for strikes and hitting them hard. Nonetheless, Severino's league average BUs and league average movement on his 4-seam FB make him out to be "more the rule than the exception" with regard to where pitchers with average BUs should let their fastballs play. It might even suggest that he would benefit from a different type of fastball such as a 2-seam. 

From Michael Augustine's Pitcher List article comparing the fastballs of Severino (top row) and Gerrit Cole.

So it got me thinking: Severino's rise-less and sink-less FB with average horizontal movement contributed to more success low in the zone, although it wasn't much success, and is a pretty effective case study for the legitimacy of how to utilize Bauer Units... I wonder how this concept would apply to someone like Craig Kimbrel?

For those unfamiliar, Craig Kimbrel is notorious for basically two things. The first is the manner in which he receives the sign from the catcher before coming set. 

The second is his ability to throw high velocity "rise-balls," or heaters that appear to end up higher than they started at release by the time they cross the plate. Obviously, it is impossible for a pitch to actually rise as it gets closer to the strike zone (no human can backspin a ball that much), but the effect of either Kimbrel's release point and/or spin seems to create this perception among hitters that the ball is "rising." Generally, this is the effect that pitchers with above average spin or high Bauer Units create.

Because I had no clue what Kimbrel's spin rate actually was, I decided to jump into the black holes that are Brooks Baseball and Baseball Savant and compare the four-seam FBs of Severino and Kimbrel. 

Here's a chart of various 4-seam FB averages from September 2018 that I used to compare:

There are a few things that can be gathered from this:

The most glaring is that Kimbrel's FB is one MPH faster than Severino's at an almost identical spin rate. Because of this, Kimbrel's BUs are actually lower, but still roughly average. 

Kimbrel's fastball is also much more effective, with an opponent's batting average that is more than 200 points lower, a opponent's slugging percentage that is more than 250 points lower, an opponent's weighted on base average that is over 100 points lower, and an almost three percent higher whiff rate. 

Combining these things with the fact that Kimbrel is a guy that lives in the upper half of the zone (more on that later), with "riseballs," this doesn't make a whole lot of sense. He also generates less vertical lift due to spin and almost three more inches of horizontal movement than Severino (probably due to his slight tilt in spin axis to the right). 

These numbers, if I knew nothing else about Craig Kimbrel but knew that Severino had average overall movement on his FB and lived low with it, would probably give me the idea that Kimbrel features some type of sinker or two-seam fastball and also lives low in the zone but is better at utilizing his strengths and fastball profile better than Severino. 

On the flip side, if I knew that Craig Kimbrel threw a rising fastball and knew nothing else about Luis Severino except these numbers, I would think that Severino also throws riseballs but can't really reign it in. 

I would be wrong. And that's why I'm not an MLB pitching coach (although it is hard to tell anything from just numbers). 

In 2017, Kimbrel, already notorious for his feature fastball, actually increased his elevated four-seam fastball usage by 15.9%, which was second in the league in that category. It led to an opponent's wOBA of .156 and a Whiff rate of 47.9%. Insane. 

So why would a guy that, by a quantitative standpoint, doesn't throw a rising fastball feature a fastball up in the zone that is described by hitters and viewers as a... rising fastball?

Luckily, while I was preparing this post, I actually came across a Twitter thread between Rob Friedman, aka "Pitching Ninja," and Dr. Alan Nathan that included an awesome .gif of Kimbrel's rising fastball... 

via Rob Friedman @PitchingNinja on Twitter 7/19/18

...followed by a brief observation of the pitch by Dr. Nathan...

...and then a link to an article by Sports Illustrated's Tom Verducci on exactly this topic posted from Friedman. 

Verducci found that in 2018, Kimbrel dominated with his 4-seam fastball yet again, posting a .171 OBA against the pitch. What went along with that statistic, however, was a little more telling.

Kimbrel released his fastball, on average, 4.95 ft above the ground that year. He was the only pitcher in the top 10 of OBA in 2018 to feature a release point that was less than 5 feet above the ground. The two next highest release points? Three-time Cy Young Award winner Max Scherzer at 5.11 ft, who finished 9th in OBA at .198, and Josh Hader at 5.15 ft who finished first with a .130 OBA. 

Take those numbers in comparison with this chart from the same SI article and you might start to figure out what's going on:

So is it Kimbrel's lower arm slot that causes the perception that his fastball rises? It's possible to believe that a lower than average release point combined with throwing up in the zone could take an otherwise normal (aside from elite velocity) fastball and make it look like it has some hop. To the hitter, this low-to-high perceived trajectory introduces a deviation from what they've seen thousands of times before. It would take some adjusting, but then again, there's no time for that when Kimbrel's job is to get 3 outs in the 9th inning. 

This couldn't be the only reason, though, could it? Maybe not. 

While perusing through Brooks Baseball and Baseball Savant trying to find statistics for my Severino/Kimbrel comparison, I started to notice something in Kimbrel's game logs from September 2018. 

In a September 5th game against Atlanta, his 4S FB spin rate ranged from 1942 RPM to 2633 RPM. 

His FB velocity that day averaged 99 mph (!!!) flat with an average spin rate of 2273 RPM, giving him an average of 22.96 BUs on the pitch. This is a below average BU measurement. Basically a sinker. 

However, the pitch that spun at 2633 RPM tallied 26.4 BUs at 99.6 mph. It spun almost 200 RPM more than the next highest-spun fastball. Now this... this is not a sinker. This is 100% your textbook riseball. 

Now, this occurred one time during the outing. An outlier. A misread from TrackMan maybe? Does he have two types of fastballs? No, no, no. Most of me wanted to believe that I had caught something. 

Hold that thought.

Four days later, on September 9 against Houston, something very interesting happened.

Kimbrel's heater ranged from 2435 RPM to 3072 RPM, averaging 2705 RPM at 99.5 mph. 

That makes for an average of 27.2 Bauer Units during the outing. Yikes. Found the rise balls. Probably looked like they had the trajectory of fastpitch softball pitches. 

Oh, he also notched the save, going three-up-three-down with 2 strikeouts.

So what happened there?

Back to that thought from earlier. 

Yes, Kimbrel was facing Houston. The Astros, seemingly out of nowhere, have staffed an army of high-spin, high velocity pitchers in recent years. Pitchers like Justin Verlander and Gerrit Cole have come to Houston and either immediately found an uptick in spin rate on their fastballs and breaking balls, or learned to utilize their natural high-spin pitches more often and more efficiently. It's been well-documented. I'd include links, but a simple "Astros pitchers spin rate" Google search will give you plenty of examples, if you're so inclined. 

The high spin in Houston is not a secret to players around the rest of the league. In fact, Trevor Bauer may or may not have accused implied that Astros pitchers were illegally applying substances such as pine tar or other sticky substances to the ball back in early 2018. 

Bauer, who professes to have never applied sticky substances to the ball in an MLB game on moral grounds, might have gone so far as to apply a sticky substance in the first inning of one of his starts early last season right around the time he made his comments about the Astros' staff. He might have been trying to prove a point, knowing the baseball world would notice the spike of roughly 300 RPM from the average on his 4-seamer during the first inning of that game. 

Well, people noticed. And although he officially decided not to comment on the matter after the start, I think he proved his point.

Was Kimbrel doing this same thing? Was Kimbrel trying to beat Houston at their own game and give them a dose of their own medicine? Maybe he was trying to match their repertoire and even the playing field? 

Who knows. 

Four more days after his outing against Houston, Kimbrel faced Toronto. This was much like his September 5th start against the Braves, where he tossed one outlier with regard to spin rate.

He averaged 97.7 mph at 2193 RPM on his fastball, placing him at 22.44 BUs. Again, this is a sinker by the numbers. 

In the middle of that, and for no apparent reason, he launched a 97.4 mph heater at 2508 RPM for a Bauer Unit measurement of 25.7. Another rising fastball out of nowhere. 

There were no other instances of Kimbrel's September 9 save against the Astros that I found. This, combined with the fact that he seemed to throw one fastball every outing that was drastically uncharacteristic of his usual repertoire, is rather odd.

I want to believe that Kimbrel applies a substance just because I want to have found an answer after all this otherwise pointless research. I know it can't be that easy, though. 

Many pitchers have marks on their hat such as Kimbrel's that may or may not be an illegal substance. More than likely, though, it's usually a combo of traditional legal (non-foreign) substances such as rosin, dirt, or sunscreen when it can be seen obviously. Who knows?

To see if his once-a-game outliers were a normal occurrence among MLB pitchers, I took a quick look at the game logs of the king of fastball spin rate in the MLB: Chicago's Carl Edwards, Jr. 

Of RHPs that threw at least 500 pitches and 100 4-seam FBs in 2018, Craig Kimbrel ranked 76th in average spin rate at 2356 RPM. Carl Edwards, Jr. ranked 1st at 2660 RPM. 

As I looked at three or four of Edwards, Jr.'s September 2018 outings, I did notice that his fastball also ranged about 400-500 RPMs per outing.

Maybe big league arms just vary that much in spin rate. Some probably vary more than others, just as some guys are more consistent with velocity or spin axis than others. Maybe Edwards, Jr. and Kimbrel both use substances, legal or illegal. Maybe there's no reason whatsoever that their fastballs range that much in spin rate. 

The point is: who knows. I can't prove that Craig Kimbrel does or doesn't apply an illegal foreign substance on a routine basis.

What it also means is that there's no way to attribute his fastball characteristics to substances, either. The arm slot take seems increasingly more valid due to the consistency, or lack thereof, of both possibilities. 

Regardless, there are two very interesting findings about this research. 

The rising effect has to at least partly, if not mostly, be attributed to his arm slot and release point. That much is for sure. Numbers don't lie on that front and there are voices around the league to back that up. 

The second is that something was definitely awry in last September's outing against the Astros. You can't attribute upticks in spin rate that are that consistent across an entire outing, even if for only three batters, to any natural cause. And for his spin rate to come back down to earth in his very next appearance? Something was up.

And I'm all for it.