Spencer Arrighetti Improved Across the 2024 Season. Can He Do It Again in 2025?
Arighetti's strikeout rate went up and his walk rate went down across the 2024 season. He is making adjustments to try to improve this season, which will be pivotal to the team having a better record.
How do the Astros improve in 2025 from what we saw in 2024? I recommend avoiding a 7 for 26 stretch, especially at the beginning of the season. A bounce back from Chas McCormick and health from Lance McCullers and Cristian Javier later in the season would certainly help. Christian Walker should be an improvement over the 1st base situation in 2024, and hopefully that will offset the decline expected in right field with Kyle Tucker in Chicago.
But I think the biggest place where the Astros might be able to improve over 2024 is in the performance of Spencer Arrighetti. Arrighetti was a battlefield promotion to the major league rotation in April due to the injuries in the starting rotation. He did not look ready, giving up 7 runs in 3 innings to the Royals on April 10, 5 to the Cubs in 3.2 innings on April 24 and 7 in just 1.1 innings to the Tigers on June 15.
Overall, Arrighetti had a 4.53 ERA in 28 starts in 2024, which was only 71st best among the 81 pitchers with 140 or more innings last season. Arrighetti was an above replacement player…but barely; he recorded 0.3 bWAR.
So why is Arrighetti a candidate to post better numbers in 2025? The answer is that he already put up better numbers in the 2024 season. In 11 starts after the All Star game, Arrighetti had a 3.18 ERA, limiting opponents to a slash line of .226/.290/.407. That’s a .697 OPS allowed.
Steady Improvement in Strikeout and Walk Rates
What made the difference for Arrighetti? The graph below shows a big part of the story. It’s a measure of Arrighetti’s strikeout and walk rate, using a 15-game rolling average. That smooths out the effects of small samples from outlier starts.
And it shows an almost steady improvement for Arrighetti in both measures across the course of the season. His walk rate went down over the course of the season, especially after June. We see similar improvement in Arrighetti’s strikeout rate, though there is a notable jump around August 1.
When one divides up Arrighetti’s season, the gradual improvement looks very stark. Arrighetti lowered his walk rate from 12.0% in the first half to 7.9% in the second half. He increased his strikeout rate from 25.4% in the first half to 31.0% after August 1st.
Those strikeouts are why Eno Sarris of The Athletic listed Arrighetti among his pitching breakout candidates for 2025.
It’s always good to bet on strikeouts. The batting average on a strikeout is zero, at least. And among starters with at least 140 innings last season, Spencer Arrighetti’s 27.1 percent strikeout rate was 15th. Ahead of Luis Gil. Ahead of Shota Imanaga. Ahead of Bryce Miller. Ahead of Pablo López.
Despite his struggles in 2024, Arrighetti was able to strike batters out in 2024 and there is every reason to think he will continue to do that in 2025.
Control Issues
The biggest concern for Arrighetti is control. While Arrighetti improved his walk rate in 2024, his baseline for walks is still very high. Over the course of the season, Arrighetti walked 10.3% of the batters he faced, third highest among pitchers with more than 140 innings pitched.
Sarris notes in particular Arrighetti’s inability to control his 4-seam fastball. “His fastball pitch chart (see below) shows he can yank the pitch sometimes and misses arm-side and up a fair amount.”
Sarris provides a note of optimism about Arrighetti’s fastball: “The good news is that command isn’t very sticky year to year and he could make an improvement here without surprising any projection system.”
So far in Spring Training, Sarris is right that command isn’t very sticky for Arrighetti, but in the wrong direction. Arrighetti has walked 12 of the 58 batters he has faced in Grapefruit League action, which is over 20% of batters. That’s moving in the wrong direction.
Adjustments to Induce Softer Contact
Those numbers are not good, but it’s only Spring Training, which means that it is both a small sample and a time when pitchers are ramping up and refining things. In particular, Arrighetti is making a two adjustments this year in Spring Training.
As Chandler Rome of The Athletic wrote earlier this Spring, Arrighetti has asked his catchers to “set up higher this spring to encourage missing above the strike zone as opposed to anywhere down and in,” where Arrighetti and the Astros pitching coaches think he gave up his hardest contact to right handed hitters in 2024.
In addition, Arrighetti is now committed to throwing a 2-seam fastball, or a sinker “to induce softer contact early in counts and increase his pitch efficiency.”
So far, those adjustments are working in Spring Training, as Arrighetti has only given up 9 hits and no homers in his 12.1 innings. He is still striking out hitters at an impressive clip, with 15 Ks so far this spring.
And thus the spring numbers show the potential for an improved Arrighetti in 2025. A pitcher who looks like the version we saw in the second half of 2024 with a modest walk rate and a high strikeout rate. Or an improved version allowing softer contact.
The spring numbers also show the concern as Arrighetti is allowing too many baserunners via bases on balls and is setting himself up for danger by doing so.
Arrighetti is the best candidate on the 2025 Astros to make a big improvement over his 2024 numbers. Getting his walk rate down was a big key to his better numbers in the second half of 2024 and he will need to do that again.