Kyle Harrison's Diminished Fastball is a Major Concern for Brewers Postseason Pitching Picture

[Jack Stern]

Image courtesy of David Banks-Imagn Images

Looking at the box score, one wouldn't think that anything was wrong with Kyle Harrison. Since returning from a month-long stint on the injured list with left forearm tightness, Harrison's results and peripherals largely matched his pre-injury dominance. Entering Monday night’s outing against the Cubs, he had pitched to a 1.83 ERA, 3.61 xERA, and 3.13 SIERA with a 31.7% strikeout rate since his return.

While Harrison’s results were nearly identical to before, his stuff was not. Before his IL stint, his signature fastball averaged a career-best 95 mph. Since his return, it’s averaged 93.7 mph. He was also unintentionally dropping his arm slot for a couple of starts, which killed some of the fastball’s carry.

The downturn in stuff made him more homer-prone – Harrison allowed 1.83 home runs per nine in his first four starts back, after a 1.08 rate before the injury – but for the most part, he was making do with what he had. Against mostly below-average lineups, the fastball was still getting whiffs at 92-to-94, and he corrected the arm slot problem after a rough outing in San Diego. Still, the velocity dip remained noteworthy.

Monday night was the first time Harrison faced a postseason-caliber lineup with his diminished fastball, and they demolished him. The Cubs, who lead baseball in runs scored and wRC+, whiffed only twice on 32 swings against Harrison’s fastball and hit four of their five home runs against the heater. Each home run pitch was under 95 mph, and three were under 94. Harrison allowed a career-high nine earned runs in 3 ⅔ innings.

Velocity wasn’t the only issue. Harrison and Pat Murphy said that he was tipping his pitches early in the outing by coming set with his hands in different positions for each pitch type.

“When you know what’s coming, it’s a little bit easier to hit, I think,” Harrison said. “So it's on me [to address] during the week. I knew these guys are looking for any sign of edge that they can get, and they got a little bit of an edge on me, I think, in that first inning.”

Harrison’s command was also poor, as three of those four fastball homers came on pitches over the middle of the plate.

However, Harrison’s fastball has been effective right down the middle at higher velocities. This season, on fastballs thrown at least 94 mph where Statcast considers down the middle, Harrison has produced a +2 run value and held hitters to a .190 batting average with a 23.6% whiff rate.

The Cubs hit fastballs in locations that have been effective for Harrison this year. Even after he tried to fix the tipping after the first inning, they still hit him hard. Above all else, the bottom line is that his current fastball is not the same pitch it was in the first half.

That also includes the pitch’s movement. When Harrison generates less velocity, he also generates less backspin on his fastball. On Monday, it averaged one less inch of induced vertical break than his season average.

“I don't think it's necessarily about the velo as much, it's about the shape,” Harrison said. “That's some of the frustrating stuff. I thought we were in a good spot last bullpen, was able to get back up to like 20 [induced vertical break], and then coming out today was more like 13.”

“It's more about not only the [velocity] number, but if the ball's taking off the way it usually does at the top [of the zone], then that makes him really effective, because it looks like it's going to be here and then it takes off,” Murphy said. “When it's not doing that, it's more hittable. We saw a little bit of that in spring training. We've seen it a few times.”

That backspin usually gives Harrison’s fastball above-average carry (which hitters often describe as “ride” or “late life”) from a low release height. When that carry is there, it hasn't become unusable around 93 mph. Instead, it goes from an elite pitch to an above-average one for his career.

MPH	Run Value	Run Value/100p	wOBA	Whiff%
94+	20	1.5	.257	29.0%
93-94	5	0.7	.313	23.7%
92-93	2	0.3	.331	28.4%
<92	-11	-2.6	.469	17.2%

In reality, Harrison’s fastball is not entirely dependent on velocity to be effective. The real issue is his limited arsenal, which becomes exposed when his fastball velocity dips. Pitchers with deep pitch mixes can get by with a merely solid fastball, but Harrison is effectively a two-pitch pitcher with one fastball and one breaking ball.

To make that two-pitch combination work as a starter, at least one must be excellent, and Harrison’s non-fastballs are not. His slider has big, loopy break with below-average spin. That kind of pitch does not play well on its own, so its effectiveness hinges on separation from an elite fastball. Harrison throws a kick changeup with significant drop as a third pitch, but he’s used it just 9% of the time this year with poor command. He threw progressively more changeups on Monday as the Cubs barreled his fastball, but he located just 21% of them in the strike zone.

Harrison’s 2024 season showed what happens when his fastball is solid instead of elite. His fastball averaged 92.6 mph that year, and it still limited hitters to a .328 wOBA with a 23% whiff rate. However, his breaking ball was hit harder, producing a .347 wOBA, compared to just .188 this year. Harrison was a below-average pitcher that season, pitching to a 4.56 ERA, 4.33 FIP, and 4.18 SIERA.

That’s not a postseason starter, an alarming twist after Jacob Misiorowski and Harrison looked like a formidable 1-2 rotation punch mere weeks ago. For most of the year, it seemed those two could give the Brewers a chance against any team in a short playoff series. Now they must prepare for Harrison to be entirely out of the mix. Logan Henderson should start Game 2 instead, and Shane Drohan and Dustin May, each of whom has his own shortcomings, will also have to cover more important innings.

Where the Brewers go from here remains to be seen. Harrison has maintained that his velocity will return.

“I'm not giving up on the velo. I think it’ll still be there,” he said. “I'm feeling great physically, so just gotta keep going, keep grinding, put the head down.”

If Harrison truly is healthy, then where did his plus fastball go, and how can he get it back?

“His delivery might be a little bit jacked,” Murphy said. “I think it's in there, and I haven't lost trust, but I think we got to go back and look at the delivery and make sure his mechanics are solid.”

Harrison and the Brewers have four weeks to get him right. How he looks during that time carries massive implications for their postseason pitching picture.

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[wallus]

Could be minor but I notice he looks like he has run a marathon by the 2nd inning in his last few starts. I know it has been hot but he looks exhausted so early in games

[JimmyC]

He simply got clobbered last night.

With May not being worthy of the trade pieces they gave up, Brewer starting pitching just got a little tenuous.