Keeping the four-seam fastball high in the zone could be the key to lowering Brad Keller’s walk rate

I had high hopes for Brad Keller coming into this season, but so far the ace of the Royals staff is having a tremulous relationship with the strike zone. Through the last two weeks of April, the league average for called balls sits at 36.4%. Keller’s mark of 42.9% puts him at third-worst out of hurlers who have thrown a minimum of 200 pitches since April 17th.

Why am I using April 17th as a starting point? Keller had three straight starts where his walks either matched or exceeded his strikeouts and is when things really started to go downhill.

Expanding this criteria for the season, Keller is ranked sixth in amount of called-balls with 37.4%. That can give us a little context for what’s going on right now and to break it down further, prior to Keller’s start on the 17th, he was working with a 36.2% called ball rate. That’s an increase of over 6.5% from his first four starts.

Using one of the more recently-developed metrics I like to reference, called strikes plus whiffs, Keller’s CSW mark of 20% is less than ideal. Now, keep in mind, Keller’s style is ‘pitch-to-contact’. For those types of pitchers (mainly of the ground ball variety), CSW rate ought to be taken with a grain of salt simply because they are not known for missing bats. Yet its important to note since his walk rate has climbed so high.

So far Keller’s 16% K-rate is right in line with his mark from last season, and is currently low enough for 7th-worst in baseball. However, within the ten lowest strikeout rates, Keller has the second-best ERA (4.07) which is behind Houston Astros starter Wade Miley (3.24).

So lets make sure that Keller isn’t being given a plethora of bad calls. Are some of his strikes actually being declared a ball? Could that be a contributor to the nearly 1-1 K/BB rate?

Out of the 289 pitches that Keller has thrown since April 17th, three were erroneously-called balls. That’s one less than the amount of pitches called strikes that were out of the zone. You’ll notice in both links that all of these pitches were on the edge of the strike zone, so its not terribly disconcerting nor does it have any impact on Keller’s perceived lack of control.

So what’s the deal with Keller’s proverbial ‘fall from grace’? The first place we should look over is release points and movement data. The latter of which might give us an idea of why he’s missing the zone so much.

Here are Keller’s 2019 game by game overly of release points with the darker images transfixed in the center being his pre-April 17th start.

For the somewhat visually-impaired, there isn’t much change to speak of. Every plot is centered around the same locale with a few stray points peeking out. Keller might be altering his arm slots, a possible trigger for mechanical issues, but they don’t deviate with any significant distances.

His spin rate data hasn’t changed much, either. Both his four-seam and sinker have RPM increases of 30 but does that make any difference?

Well, with Keller’s four-seam fastball it might. Pre-April 17th starts have his spin rate averaging 2289 RPM. From April 17th, it jumps to 2318. That puts the pitch in a different whiff rate expectation.

In terms of velocity, the four-seam has lost just .3 MPH (94.2-93.9) and rounding both figures we still have a 94 MPH fastball.

Keller’s sinker has gone from 2047 RPM up to 2077 with a half a mile per hour drop and, like his four-seam, doesn’t create any velocity difference when you round the numbers (93.4-92.9).

Looking at the chart below from Driveline Baseball, the anticipated swinging strike rate from 21-2300 RPM to over 2300 RPM increases by 2%. In this case, his sinker stays entrenched where it’s at.

As it stands now, Keller’s swinging strike rate is 6.8% on his four-seam and his sinker rate is 2.7%. Again, this is to be expected for a pitcher of Keller’s pedigree and evaluating with this chart is more to observe how these changes could effect pitch efficiency.

With that aside, lets turn to movement data. The big change only lies within his slider metrics.

Comparing his first four starts to his last three, Keller’s slider is dropping an extra 3 inches vertically and almost a quarter of an inch horizontally.

Looking closer at the slider, there is a 6-degree adjustment in spin axis. Keller has gone from around 64-degrees to a slightly more side-spin friendly 58-degrees. However, this is a pretty minor tilt and I’d venture to guess that his almost one mile per hour drop off the slider velocity is more responsible for the additional break than anything else.

The only other notable change in movement is Keller’s sinker is dropping an extra inch since his first four starts. Keeping that pitch lower in the zone will help with missing bats and even further inducing ground balls.

Keller still excels at mixing his pitches well, with his ‘out pitch’ remaining the slider, which has seemed to improve a bit as the season progresses. Right now, Keller’s CSW on the slider is around 27%, which is pretty good. And he needs to be in a position to use it more effectively as it draws a 38% whiff/swing rate.

The key to making that happen is a productive fastball, his least effective pitch this season. Keller is one of the better pitch tunnelers in baseball, especially with his fastball/slider combo. Even his sinker (middle pitch) can get in on the action.

Focusing the four-seam up in the zone is a religion to me. Keller needs to keep the four-seam elevated and leave the mid/low zones for the sinker (as exemplified in the gif) and I’ll explain why.

First, a few good examples of Keller going high in the zone with the four-seam.

Now, lets see where Keller has been putting his four-seam fastball this season.

Keller seems to favor running the pitch in to the left hand side of the plate albeit the majority are landing in the strike zone.

Observe the results of each pitch in the chart below.

Its a little hard to see but concentrate your attention to the pinkish dots. What do you notice? Those whiffs seem to occur at almost exclusively at the top of the zone, where Keller is throwing only about 25% of the time.

Keller has located the pitch at the top edge/shadow and upper ‘chase zone’ (the area just above the edge/shadow) 65 times with a 44.6% called-ball rate and an essentially identical called-strike rate (+0.1%). Just two of those pitches ended up hits.

We don’t want to get caught up in hits allowed too much because Keller’s four-seam batting average against is just .241 with a .250 BABIP. Contact isn’t the problem for Keller, its the walks that do him in.

Including the chase zone in this instance is what evens out the balls and strikes for him. Hitters seem to be aware that they don’t have to swing at the fastball much because Keller’s control is coming into question.

However, if we shift our focus to the upper edge/shadow and include the inner, upper portion of the zone, the results are much different.

Notice that only eight of the 76 pitches thrown to the upper zone were taken for strikes.

While Keller throws a lot of pitches out of the zone, there really aren’t a lot of situations where he’s forced to throw a strike in relation to other counts.

Returning our attention to the much more effective edge/shadow and upper strike zone, Keller threw 50.5% of his fastballs to that location through his first four starts. The last three? Just 16.3% of the time.

Does that make my conclusion that Keller needs to keep his four-seam high in the zone concrete? Not necessarily because we don’t know a lot about his command which is directly related to intent. Looking at this chart which plots all of Keller’s elevated fastballs (chase zone, edge/shadow, and high strike zone), we see that pretty much all of the pitches he threw there were pretty well located.

However it does appear that there is some correlation between his lack of attacking high in the zone along with his degraded K/BB-rate and performance in general. A change in location focus could result in more strikeouts, or even more ground ball contact (especially if you can take advantage of ‘launch angle hitters’). But more importantly it could help bring down his walk rate by forcing more pitcher's counts where he can then start wiping hitters out with that great slider.