Zack Greinke's Strikeout Rate is Way Down; His Performance Has Followed

The comeback on Sunday was awesome, as rookie outfielders Jose Siri and Chas McCormick hit back-to-back home runs in the 8^th to turn a 6-4 deficit into a 7-6 victory.

But what was worrisome was that a comeback was necessary at all. The Astros fell behind in the game because Zack Greinke had a bad start—giving up 5 runs over 4 innings while allowing 5 hits, 1 home along with 3 strikeouts and 1 walk. It really fell apart for Greinke in the 4^th as he gave up 4 singles, with a walk to Astro killer Kole Calhoun.

The bad outing by Greinke has unfortunately become a common occurrence. Greinke gave up 8 runs (7 earned) in 5 innings on Tuesday of last week in Arlington. Greinke took the loss in that start, as he had in his previous two starts in late August.

In fact, Greinke’s season seemed to turn on July 31, when he was shelled in San Francisco. Greinke gave up 6 runs and 4 homers in 4 innings at Oracle Park.

The chart at the right shows Greinke's stats before that start in San Francisco. Greinke had posted a low WHIP and low OBP against, in large part because he allowed few walks. Since July 30, Greinke has maintained a low walk rate. 

But in his 8 starts since then, Greinke has cratered. Greinke has been hammered, giving up 11 home runs--one every 4 innings pitched. Greinke gave up 17 homers in 121.2 innings before July 30, a rate of about one every 8 innings. Greinke gave up a slugging percentage of .382 before July 30, and .527 after it. The average batter went from having the slugging percentage of banjo-hitting middle infielder (e.g. Nicky Lopez has a .379 SLG; Cesar Hernandez has a .386 SLG) to that of middle of the order slugger (Teoscar Hernandez has a .529 SLG; Aaron Judge and Rafael Devers are at .532). 

The other stat that declines precipitously for Greinke is his strikeout rate. In the first three-plus months of the season, Greinke struck out 18.4% of the batters he faced. The MLB's K% this season is  23.2%.  But Greinke's strikeout rate has declined to 13.2% of all batters that he has faced. 

Overall, Greinke's strikeout rate is 17.0% for the entire season. Baseball Savant ranks that in the 9th percent of all of baseball. 

While the late-career Greinke that we've seen in his two-plus years in an Astros uniform has diminished velocity from prime Greinke, he as still able to strikeout a sufficient number of batters. The chart at the right shows Greinke's K% for every season of his career in blue, and the grey line shows the MLB average. The chart looks like a "One of These Is Not Like The Other" segments from Sesame Street. After being well above league average in his prime and above league average in his previous 3 seasons, Greinke's K rate has declined and declined hard in the 2021 season. He's clearly not the pitcher he was in his prime, and is not even the pitcher he was in 2019 or 2020. 

And Greinke's K rate has declined over the course of the season. The graph at the right shows Greinke's the 15 game "rolling average" of Greinke's K% and BB%. Greinke has maintained his low BB% (his rate is 5.2%; the MLB-wide rate is 8.7%), but his K% has declined over the course of the season. He is striking out fewer batters than he did in 2019 and 2020 and that rate is declining throughout the season. 

The lack of strikeout leaves Greinke more vulnerable to batter ball luck, like we saw on Sunday when Diamondback hitters kept finding holes in the Astros defense. But when you combine the lack of swing-and-miss in Greinke's game with the increased home run rate, and you have the recipe for a declining pitcher we have seen over the last month and a half. 

The decline in Greinke's performance leads to the question of whether he should pitch in the playoffs, or even start a game. In projecting the Astros playoff roster in an article on Monday, Jake Kaplan of The Athletic had Greinke listed as the Astros Game 4 starter. But Kaplan's logic in plugging Greinke in to start after McCullers, Valdez, and Garcia has less to do with Greinke and more to do with Jose Urquidy.

Kaplan wrote, "I believe the Astros, operating with an all-hands-on-deck mentality, might leverage [Urquidy] out of the bullpen in their effort to win Game 1 or Game 2...If Urquidy pitches early in the series, he could impact two games instead of one. Deploying Urquidy in relief could allow the Astros to bypass their shaky middle relief in one of these two first games."

"If Urquidy does make a multi-inning relief appearance early in the series, Greinke would then be the fallback Game 4 starter, if necessary...Because I think the Astros will use the best-of-five format to be creative with their pitcher usage, I still project Greinke to be in there at the back of a four-man rotation."

Maybe so?  I can certainly see the case for Urquidy being a useful multi-inning weapon out of the bullpen, especially in a scenario where Cristian Javier does not make the playoff roster (which is what Kaplan projects). 

But leaves the potential that the Astros are down 2-1, playing a must-win game on the road at the Comiskey Park replacement, and relying on Greinke to wake up the echos and pitch like its 2009 again.  Heck, we'd take 2020 again, and hope for 2 runs over 5 innings and rely on the bats to outslug the White Sox. 

But with a strikeout rate this low, it's hard to trust Greinke right now, and with two weeks left in the regular season, the playoffs are just about right now.