Wily Peralta will need a better fastball to succeed

Wily Peralta is having a good spring so far with a 7.4 K/9, a 1.09 WHIP, and a 1.23 ERA in 7.1 innings. His opponent quality (OppQual) is 8.5, so he’s thrown against some good competition. He got his first save of the spring against the Chicago Cubs last night, allowing one hit that plated an inherited runner along with a walk but no strikeouts. The glaring concern continues to be the high walk rate - four walks to just six strikeouts. Since Peralta’s walks were also plentiful last year, are we in for another spotty season from the Royals (potential) closer?

Since it is inopportune at this point to make weighty assessments on how Peralta will attack hitters this season, we can take a look at what issues arose in 2018 and see if Peralta is able to correct them going forward.

To suppress any initial doom and gloom, Peralta has some things working for him. His slider is pretty good and he increased his changeup use. The off-speed pitch ended up being his best last year according to Pitch Info Pitch Values (2.9 wCH).

The changeup also drew Peralta’s highest swing rate (61%) and also produced the most whiffs of his four pitches (19%). To give a little perspective, Peralta threw the pitch just 11% of the time and primarily used it against lefties. I’d love to see him use it more this year.

Peralta’s primary pitch was the fastball, of which he equally threw the two-seam/sinker and four-seam variety. Below is an example of how the slider and changeup work with Peralta’s fastball.

Peralta’s fastball averages around 97 MPH. Being able to throw that hard immediately puts him at an advantage over other pitchers. On the flipside, Peralta had a really low spin rate on his four-seam last year. His 2100 RPM was on the lower end of baseball last year (minimum 300 pitches). Somewhere around 2300 RPM is the league average.

Low spin rate on a (four-seam) fastball can be a issue depending on what the goal of the pitch is. In this chart from a Driveline Baseball research article published earlier this year plots whiff rate by spin rate and velocity. Keep in mind Peralta’s figures when inspecting.

Notice that at 96-98 MPH, a spin rate in the 19-2100 rage should yield a 10% whiff rate. Yet in 2018, Peralta caused hitters to miss his fastball at a rate of only 5%. What’s more, when hitters did make contact on the four-seam, they were pretty successful (.333 BAA). The two-seam/sinker was only a slightly different story (.313 BAA).

To be fair, the BABIP on those pitches were high, indicating that perhaps Peralta was the victim of some bad defensive luck. The Royals defense, in terms of defensive runs saved, deems them league-average.

His xwOBA (expected wOBA) vs. his actual wOBA creates a modest argument against the luck assessment. The difference between what was expected and his actual wOBA on the fastball was about 21 points lower. Disparities of 100 points or more would be more likely to indicate regression (good or bad) the next year. We could say, for the most part, that he got what he deserved (for lack of a better phrase) with the pitch.

So was the issue with location? Below maps out where Peralta typically went with his fastballs followed by average exit velocity by zone.

This data coincides with the fact that Peralta’s overall hard-hit rate (Hard%) last year leaped nearly 15% above his career average of 30%.

Peralta kept his fastball out of the zone around 53% of the time, much higher than the league average of 46%, which was likely for good reason. You can see that when the fastball did end up in the zone, it was walloped. What’s more is hitters whiffed just twice on fastballs in the strike zone. With a high-90s fastball, that’s hard to understand.

So was it sequencing? I can’t see how. Peralta did a good job mixing his pitches last year.

And while the two-seam/sinker saw some temporary improvement, his fastballs got worse as the season went on. You can also see a degraded performance correlation when looking at his fastball whiff trends.

While this all sounds pretty bad, we shouldn’t come down on Peralta too hard. The former starting pitcher gave us an incredibly small sample size in 2018 so its hard to glean future value out of what he did. It’s easy to say all Peralta has to do is increase his spin rate on the four-seam. Improving spin rate directly correlates with more swing and miss stuff as evidenced by the whiff rate chart from Driveline.

I have to wonder if that adjustment would actually improve the pitch for him.

Peralta’s overall command isn’t great. According to Baseball Prospectus’ command metric (CMD), he’s ranked well below average with a score of 40. So was his delivery erratic? There doesn’t seem to be anything mechanically off as his release point spread is minimal. If nothing else, his arm slot got progressively lower through the year.

So the issue might in fact be lack of command and control of the strike zone. Let’s look at a couple of examples. Here’s a fastball that catcher Salvator Perez wanted low. Peralta (we assume) mistakenly threw it high and, well...

From the screenshot, we see where Perez’s glove was initially positioned.

In the next example, Peralta wasn’t off by much but still hung the pitch. Luckily for him, the Detroit Tigers’ Jeimer Candelario barely missed rocking the pitch and drove the ball into the ground for a double play.

Below might be the worst example of Peralta missing his spot. Again, he got a break because the Tigers’ Victor Martinez missed tying the game by just barely swinging under the 98 MPH fastball.

Another look at the desired location for the pitch, which ended up nowhere near Perez expected it.

Peralta’s best bet is to ditch the four-seam and focus on the two-seam/sinker. Unless he can make changes to improve his spin rate (which isn’t likely), he’s much better off using a two-seam/sinker. It has better movement and is thrown harder in relation to others who throw the pitch, even more so that his four-seam. Peralta’s whiff rate on the pitch is much better than league average. It induces a lot of ground balls and doesn’t come with the slugging risks that the four-seam does.

Peralta seems confident in what’s come in 2019. In an article by Lynn Worthy from the Kansas City Star, Peralta spoke on his perspective as a late-inning reliever:

“It’s way different, so you have to come in and attack the strike zone,” Peralta said of his approach as a closer. “There’s no time to mess around because you know it’s one inning. You go all in, all that you have, trying to get three outs as quick as you can. You know probably the next day you’re going to be in the game too.”

That mindset will be important because, in terms of leverage, Peralta seems to excel when the pressure is on. That’s exactly what you want from a setup/closer. If he manages to stay in either of those roles, I’d really like to see his K/9 reach at least 10-12 (he was at a little over 9 in 2018) and that walk rate has to come down.

By removing the four-seam and replacing it with a seemingly effective changeup along with his knockout slider, we could reasonably expect an uptick in performance and a much more comfortable pitcher. If his fastball control can be harnessed (which may give him more confidence in his repertoire), Peralta could fast become one of the best closers, let alone relievers, in baseball.