Astros starting pitcher Mike Burrows has been having a tough time with the home run bug. Currently he is tied with two other pitchers (Brady Singer and Shota Imanaga) with 17 HRs, second behind Jameson Taillon (20 HR).
Burrows’ weakness is against lefty batters and teams tend to load up their lineups with LHBs against him. 12 of his 17 home runs were given up to left hand batters. He is tied with Zack Littell, Singer, and Jameson Taillon with most home runs surrendered to lefty bats. As I previously explained (“Astros’ High Walk Rate is Caused by LHB”), Burrows walks way too many LHBs, and unfortunately this causes a sequencing issue when those walks precede a HR. 11 of his 17 home runs occurred with runners on base, which leads the league and results in maximum damage from the home runs. Other pitchers with the home run bug, such as Singer, Imanaga, and Taillon, were more likely to surrender solo home runs. Similar to the poor sequencing luck, Burrows also has given up the second most HRs (6) on two strike counts.
Home run rates tend to be volatile among pitchers, which reflects some degree of randomness from year to year. The extent of this randomness probably reflects the fact that individual hitters have more control over HRs than pitchers. As a gross approximation, pitchers’ home run are expected to regress toward the league average HR/fly ball rate. Burrows’ HR/fly ball rate currently is 17.1%, which is much higher than the league average of 10% – 11%. The “x-FIP” statistic reflects league average HR/Fly ball, and is often used to exclude assumed home run flukiness. Burrows’ x-FIP (4.68) is approximately one run less than his ERA and FIP (5.75 – 5.77). In addition, both x-ERA and SIERA are stats that also are based upon excluding “luck.” Burrows’ x-ERA and SIERA are similarly about one run less than his ERA and FIP, with values of 4.63 and 4.60, respectively. So, we probably should expect Burrows’ ERA (and related HR rate) to regress in the direction of 4.60.
When the Astros traded for Burrows, they probably were attracted by his 3.94 ERA with the Pirates last year. But Burrows has a significantly higher HR/fly ball rate with the Astros (17.1%) than he did with the Pirates (12.9%). Burrows currently has given up 17 home runs which is more than the 13 homers he gave up all last season as a Pirate.
The number of home runs is affected by the dimensions of the ball park. Moving from Pittsburgh’s PNC Park to Houston’s Daikin Park is an important factor. PNC Park has one of the more spacious left fields and the LF dimensions are more forgiving to pitchers’ propensity to allow home runs. Daikin Park has the shortest left field dimensions, and the Crawford Boxes are the most welcoming distance for home run hitters. So, to some extent, the Astros should have anticipated some increase in Burrows’ HR rate. As it turns out, RHB home runs predominantly landed in the Boxes and LHB home runs predominantly were hit to CF and LCF.
Baseball Savant’s Statcast provides analyses of expected home runs based on the the interplay of distance, exit velocity, and launch angle with each of the MLB’s ballparks. The Savant chart below shows Burrows’ home run totals if the homers had been hit in each of the 30 stadiums.
Burrows would have seven fewer home runs if he had played his games in PNC this year. Burrows would have two more home runs if he had played all his games at Daikin this year. In terms of the home runs allowed by Burrows in 2026, Daikin is the least forgiving (19 home runs) and only two ballparks would have allowed fewer home runs than PNC (10 home runs). Based on this comparison of the specific home runs allowed by Burrows, Daikin allows almost twice as many of those homers as PNC Park.
Statcast also gives us information on whether home runs were “no doubters” or “doubters” (i.e., barely clearing the fence) and derives an “expected HR.”
According to the Statcast evaluation, Burrows was somewhat unlucky on the batted balls that ended up as home runs. Burrows’ expected home runs are four less than the actual home runs (HR-xHR). Last season with the Pirates, 65% of Burrows’ home runs were “no doubters” but only 35% of his current home runs are no doubters. For the borderline home runs, some degree of luck may affect whether a ball falls over or just short of a HR. Aside from the change in ballparks, Burrows also appears to have been a little unlucky on the borderline home runs.
The majority of home runs allowed by Burrows (11 of 17) have been hit off the 4 seam fastball. While the Astros have limited Burrows’ use of the 4 seamer against RHBs, the 4 seamer is used more frequently against LHBs. The movement of Burrows’ sinker isn’t useful against LHBs, leaving the 4 seam FB as the only “hard” offering against lefties. The impact of the HR bug becomes apparent in the remarkable .781 SLG associated with Burrows’ 4 seamer. But the 4 seamer has been problematic, whether Burrows is a Pirate or an Astros. We can compare the “expected” stats for Burrows 4 seamer in 2025 and 2026:
x-BA 2025: .298 2026 .319
x-SLG 2025: .540 2026: .630
While the results are incrementally worse this year, the 4 seam fastball still was a poor offering in 2025. According to Stuff+ Burrows 4 seam fastball is better in 2026 than 2025 in terms of physical characteristics: 99 Stuff+ in 2026 vs. 86 Stuff+ in 2025.
The sinker, which Burrows uses as his main fastball pitch vs. RHBs, has produced much better results in 2026 than 2025, as shown below.
x-BA 2025: .351 2026 .285
x-SLG 2025: .501 2026: .393
These two hard pitches team up with Burrows’ change up, generally viewed as his best pitch. While the change up was praised as practically unhittable in 2025 (.164 x-BA and .253 x-SLG), that put away pitch hasn’t been as good in 2026 (.219 x-BA and .299 x-SLG). The change up continues to be a good pitch, but it’s not as dominant as it was in 2025. It’s hard to know whether this slight dip in the dominance of the change up has a domino effect on fastball effectiveness.
Between the smaller strike zone (which I discussed here), deterioration in batted ball luck, different more challenging ballparks, notable bad luck on HRs falling in, and opposing teams concentrating LH bats in the lineup, Burrows has faced somewhat of a perfect storm.
I would expect some degree of favorable regression as the season progresses. Efforts to limit future home runs should probably focus on the 4 seam fastball versus left hand bats. That could take the form of improving location precision (staying away from the center zones and more toward the upper and lower corners) or even more extreme measures such as substituting a cut fastball against lefties (as suggested by Cody after Sunday’s game). In any event, reducing walks is always very helpful, suppressing traffic on the bases in front of home runs.
Feature photo from @astros on X, Source Link.
Great stuff as always, Clack!
Nice work, Clack. As you mentioned, it’s not even so much that he’s allowing HRs so much as he’s allowing baserunners before his HR. JV allowed the 3rd most HR in MLB in 2019 and won the Cy. A lot of it because 28 of his 36 HR were bases empty shots.
Astros need to figure out their pitching to LHB problem pronto across the whole staff.
Great analysis. I have to say though, one of the parks where the xHR is lower (Colorado) definitely wouldn’t be the case IRL. I would not want Burrows pitching to LHBs in Coors. There would be a 500ft moonshot in there somewhere.
In addition to what others have said:
-That’s two starters with great stuff on their 4SFBs who have absolutely imploded in MLB this year for us. IIRC, Weiss’s 4SFB also rated a bit better with us in his time on the big club, but produced similar results in being clobbered by hitters (as well as walks, and weakness to LHBs).
-I don’t know that Burrows lasts in a 5 man rotation if the team ever moves to one. Other starters have issues or regression potential, but the combination you note- Burrows’ current weakness to LHBs plus tendency to walk batters before giving up HRs- makes him the weakest link, IMO. Plus he is optionable without much consequence due to his limited service time.
-Brown (ace)
-Arrighetti (potential regression based on xstats), LHB struggles)
-Imai (adapting to MLB)
-Lambert (minor potential regression based on xstats)
-Teng (struggles 3rd time through the order)
-Burrows (potential positive regression, least capable at dispatching LHBs, prone to rapid meltdowns)
Right now, he is the odd man out, IMO.
Chandler in his piece this morning says he feels like Burrows has a long runway. Not just with the 6 man rotation he anticipates the Astros using soon, but also because Dana traded Melton and Brito for him. Dana seems like he doubles down on any player he spends capital to bring in.
I don’t doubt it but it’s a bad reason and IMO one checkmark against DB staying in a GM role. No different than owners who won’t change playing time for a bad contract player because they spent money on them, the job of an owner and a GM is to win games and acknowledge the money spent (or trade capital invested) as a sunk cost the moment the deal is done.
It wouldn’t surprise me to see Burrows hang around and continue being as unserviceable as, say, LMJ last year or Javier this year, simply out of pride or displaced fear on Dana’s part.
I just don’t see any way to make the adjustments he needs in season.
Yeah, don’t trust the Coors x-HR. Note that I used the Standard version which is based on LA and EV to establish distance, excluding environmental factors. The most notable stadium environmental factor is Coors Field.
Looking at his savant page, there’s also another thing that sticks out like a sore thumb (to me anyway).
His arm angle is drastically changed from the last 2 seasons….
He went from a 50 degree angle, to 48 degrees last season, and this season it’s down to 39 degrees.
That seems incredibly drastic in just a 2 year span.
Would this be a factor as well?
Yeah I wrote about that last week here. I think it plays into making lefties track his pitches easier
I think “lowering the arm angle” is part of the Astros’ tool box for improving pitchers. Spencer Arrighetti is a pitcher who showcases the lower arm angle. It helps add more deception for the fastball. But I also have to wonder if it creates more control problems.
It’s beyond my knowledge but I wonder if the lower arm angle primarily benefits 4SFB (to create the illusion of rise) as opposed to primarily benefitting tunneling. If it helps tunnel pitches better we probably should keep doing it routinely, but I don’t see that the “rising FB” strategy can sustain itself for most pitchers with the new zone.
I know the Astros generally prefer funky/weird arm slots too, IIRC. Maybe there are other tweaks which can be made to raise, lower or otherwise play with a pitcher who has a predictable/middle of the road delivery.
I have seen the effect of low arm angle described as “making the fastball appear to explode on the hitter.” So, the ball appears to get there faster than the velocity indicates. Maybe it’s adding the illusion of “hop” to the fastball. However, I think it requires more strength by the pitcher to keep repeating the low angle mechanics, which is why I wondered if it makes control more difficult.