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Miles Mikolas and the struggling slider

The Lizard King made his money on his slider in 2018, but the pitch has been far from effective this season.

Los Angeles Angels of Anaheim v St Louis Cardinals Photo by Dilip Vishwanat/Getty Images

Miles Mikolas was the unexpected gem of the Cardinals’ 2018 season. He was the only starter to finish the season with more than 200 innings under his belt, finishing sixth in the NL Cy Young voting.

A 4.3-fWAR season with a 2.83 ERA and 3.28 FIP led Mikolas and his stingy pitching to a four-year, $68M extension, looking like he would be a staple at the front of the rotation for most of that time.

What happened?

Mikolas hasn’t been terrible overall. With 1.1 fWAR through 99.1 innings, he’s on pace to be roughly a two-win player. But for comparison, Sandy Alcantara has been worth 1 fWAR for the Marlins this season with just two more innings pitched.

Mikolas has seen a little bit of a dip in his K-BB%, but not much. His strikeout rate went down a tenth of a percent, from 18.1% last season to 18% in 2019. His walk rate went up from 3.6% to 4.1%. Obviously not helpful, but not worth being half as productive as he was last year. In fact, that low of a walk rate puts him in the top 6% of the league, according to Statcast.

The raw data for the type of balls in play coming off of Mikolas is largely unchanged, as well. His line drive rate didn’t change at all, holding at 22%. His GB/FB ratio went from 1.73 to 1.66.

Looking at his surface numbers, there’s really only one thing on a stats page that jumps out, and has some underlying metrics that may correlate: home runs.

To start, Mikolas’ HR/9 has doubled. He’s given up 16 home runs this season, the same number he surrendered in all of 2018.

According to Statcast, Mikolas’ Hard Hit % has jumped 6.5%, now at 35.7%.

Looking at his pitch values between last season and now, it seems the blame might fall on Mikolas’ slider.

In 2018, the Lizard King’s slider was second-best among qualified starters when standardized over 100 pitches. It was worth 3.06 wSL/C, second only to AL Cy Young Blake Snell (3.97). This season, his wSL/C is -0.97, putting him 48th among qualified starters.

All of his other pitches (aside from the sinker) have decreased in value as well, but that’s to be expected when a player’s most valuable pitch falls off entirely. And none have decreased to the level which the slider has.

That’s the real effect of a knockout pitch like his slider falling off – only five of his 16 home runs surrendered have come off the slider, but it weakens the rest of his repertoire.

He’s even thrown the pitch a little less this year, with an increase in sinkers.

Mikolas has seen a change in release point this season, moving everything a bit closer to an overhand delivery (to his left-hand side). Here are some graphs from FanGraphs showing the release points year-to-year for all pitches, and just the slider specifically:

That change has corresponded with some pretty rough numbers for Mikolas’ slider. Below is a chart from BrooksBaseball, showing the increase or decrease in numbers for Mikolas’ pitches between 2018 and 2019. Negative numbers on vertical categories indicate a drop, where as positive numbers indicate a “rising” effect. Negatives with horizontal categories move toward the right-hand batter’s box, and positives move toward the left-hand box.

Miles Mikolas, Changes in Pitches, 2018-2019

Pitch Velocity (MPH) pfx HMov (in.) pfx VMov (in.) H. Release (ft.) V. Release (ft.)
Pitch Velocity (MPH) pfx HMov (in.) pfx VMov (in.) H. Release (ft.) V. Release (ft.)
Fourseam -0.65 -0.92 0.34 0.19 -0.04
Sinker -0.27 -0.64 0.07 0.18 -0.01
Change -0.3 -0.21 -0.45 0.22 0.01
Slider -1.14 -0.01 -0.85 0.27 0.02
Curve -0.43 -0.04 -0.74 0.22 0.04
data from

Mikolas’ slider is the only pitch to drop more than one mile per hour in terms of velocity. It’s also seen nearly an inch more drop toward the plate compared to 2018’s movement, while barely changing in terms of horizontal movement.

Combined with a change of nearly three inches in horizontal release point, that doesn’t spell good things for his slider.

This piece is less of a concrete diagnosis and more of a general practitioner noticing something off and suggesting a specialist take a look. Miles Mikolas made his money on his slider, one of the best of the league. This season, a change in release point and a noticeable difference in movement and velocity have turned it into a pitch with less effectiveness, weakening the whole repertoire in the process.