The Astros’ starting rotation was riddled by injuries in 2023, and to some extent, continues to be affected by those same injuries. Given financial constraints, I will be surprised if the Astros make any off-season moves to improve the rotation. So, it’s really important for the 2023 starting pitchers to improve in 2024.
When most people talk about 2024 rotation concerns, they mention Verlander’s age or Valdez’s performance drop-off in September and October. But we have a huge body of experience with Verlander and Valdez. For that reason, they aren’t the biggest question marks. Maybe I can surprise you by suggesting that Hunter Brown’s performance will be a key to the rotation’s effectiveness.
Why is Brown so important? Lance McCullers, Jr. and Luis Garcia cannot be expected to pitch starter innings until late in the 2024 season—if at all. Cristian Javier is coming back as the No. 3 pitcher, and his post-season pitching indicates that he may be capable of returning to his fine 2022 form. But, to be fair, Javier’s spotty 2023 performance leads to notable uncertainty as to whether he will pitch like a No. 3 starter.
Hunter Brown doesn’t need to pitch like an ace in 2024. But it’s important that he improves over his disappointing 5+ ERA in 2023. If Brown can pitch like a solid mid-rotation starter (3 or 4 slot), he will provide a stable bridge between the Verlander/Valdez/Javier top of the rotation and the No. 5 pitcher, who could be some combination of J.P. France, Brandon Bielak, or Jose Urquidy. Why is Brown the key, and not France, Bielak, or Urquidy? Put simply, Brown is the more talented pitcher with better raw stuff. For example, compare the 2023 SIERA for France, Bielak, and Urquidy (4.95, 5.05, and 5.34, respectively) to Brown’s SIERA (3.70).
Brown exhibits exceptional talent for a young pitcher, and it’s important for the Astros to help him convert that talent to results. According to Stuff+, Brown has the third best stuff in the rotation (104), behind only Verlander and Valdez (both 106). Baseball Savant’s top five most similar players to Brown, based on movement and velocity:
That’s an impressive group of pitchers on Brown’s comparables list. Four of the five ranked highly in the Cy Young Award voting.
Brown’s 2023 season was a tale of two seasons. In the first half, Brown was effective and his ERA was among the best in the Astros’ rotation. In the second half, Brown’s ERA increased dramatically. Brown’s ERA increased monthly until the results became clearly untenable by Sept./October.
I agree with Cody Poage’s view that workload was a significant contributor to Brown’s rapid decline in performance over the year. Brown pitched a career high number of innings in 2022 and then came back in 2023 with an even higher inning workload. Brown’s 155 innings was the second highest workload among rookie starting pitchers; if Kodai Senga— a 30 year old veteran pitcher from Japan—is excluded from the rookie list, Brown’s workload far exceeds all rookie pitchers. In the second half of the season, Brown’s fastball velocity frequently declined after his first or second inning.
Hunter Brown also allowed high exit velocity contact. His average exit velocity and barrel percent both were worse than all but 8% - 9% of major league pitchers. The increase in exit velocity over the course of the season led to a 44% increase in his SLG percent between the first and second half.
Pitcher exit velocity is somewhat repeatable as a performance characteristic. However, pitchers can mitigate the damage from hard contact by producing high groundball rates. Brown at his best is groundball-heavy, with batters smashing knuckle curves and sliders into the ground. However, Brown’s very good groundball rate declined in the second half (from 55% to 48%). Perhaps he lost some of the sharp break on his curve and slider in the second half of 2023.
With his high exit velocity rate and declining groundball rate, Brown allowed 27 home runs. In the first half of the season, Brown avoided much of the HR damage—67% of the HRs were hit in the second half of the season. HR rate is both volatile and noisy from season to season. x-FIP is used to measure the potential for future regression in HR / Fly rate. Brown’s x-FIP is 3.52—much more reasonable than his 5.09 ERA.
In the past, scouts have said that Brown’s ceiling will depend on his ability to throw strikes. His control also deteriorated in the second half of the season. In the first half, 57% of his pitches were balls; the ball percentage grew to 66% in the second half of the season.
As the season progressed, the Astros appeared to push Brown to throw more 4 seam fastballs at the top of the zone—one of the team’s favorite approaches to fastball pitching. And that seems like a good idea, because it “tunnels” the contrasting location of the fastball with the downward movement of the slider. However, the 4 seam fastball missed the mark too often in the second half, producing fastballs near the heart of the zone. This may explain why Brown’s 4 seam fastball was especially vulnerable to HRs.
POTENTIAL FOR IMPROVEMENT IN 2024
Maybe the question about 2024 boils down to whether Brown can pitch more like the pretty good first half of 2023 instead of the worse second half. However, there are reasons to expect the more optimistic outcome.
First, if excessive workload contributed to the second half decline, as we surmise, that is correctable. If Brown’s workload can be more carefully controlled and managed, hopefully he can avoid the second half swoon. The Astros should happily prefer 140 innings of good pitching to 160 innings of bad pitching.
Second, the Statcast “expected” statistics all indicate that Brown’s results should have been much better. As a result, beneficial regression may lead to improved results in 2024. The more favorable “x-” results are compared to actual results, below.
ERA Actual ERA 5.09 / xERA 4.27
wOBA Actual wOBA .340 / xwOBA .318
SLG Actual SLG .456 / xSLG .414
Home Runs Actual HR 27 / x-HR 23
Fangraphs SIERA 3.74 / Actual ERA 5.09
According to the Statcast metrics, if Brown had been luckier, his statistical results would have been more in line with a middle rotation starter. These “x-” results are indicative of potential favorable regression, compared to 2023.
Third, the Steamer and ZIPS 2024 projections both foresee improvement in Brown’s statistical results.
ZIPS Projection: ERA 4.06 HR 16 WAR 1.8
Steamer Projection: ERA 3.78 HR 16 WAR 2.5
Note: Brown’s 2023 bWAR is 0.1
The Steamer projection is somewhat more bullish on Brown’s pitching. But the results for either projection system are consistent with the expectations for a No. 4 or 5 starting pitcher.
Given the overall background, I don’t think it’s a stretch to say we should expect substantial improvement from Hunter Brown in 2024.