Astros’ Status: Pitching Edition

“What’s WRONG with the Astros?” We hear this refrain when the Astros get off to a slow start to the season. The tendency is to blame the pitching staff. We remember the bullpen blowing leads and the starting pitchers struggling to go deep into games. But I think the stats would tell us that the pitching has not been that bad.

One of the reasons it feels like the pitching has been bad: the pitching was so, so good in 2022. Last year, the starting pitching and bullpen were nails when it came time to win low-scoring games. The pitching often compensated for the periods when the offense slumped. By comparison, the Astros pitching so far hasn’t dominated to the same extent as 2022. But, as I’ve written previously, the 2022 pitching was so exceptional that some degree of regression is expected. It’s early in the season, but still the pitching hasn’t been that bad.

Let’s start off with the fact that the Astros are ranked with the sixth-lowest ERA in baseball (3.46). Only Minnesota, Tampa Bay, Milwaukee, Yankees, and Cubs are better. SIERA is a more advanced measure of pitching, and the Astros are ranked with the sixth-best SIERA (3.85), one-tenth of a point behind the Rangers and five-tenths of a point better than the Dodgers.

And there is some evidence that the pitching issues are partly related to bad luck with BABIP. In theory, pitching results in small samples should regress toward average BABIP. The Astros pitching BABIP is .307. The pitching BABIP ranks 8th worst in the majors. The current league average BABIP is .297. Sure, BABIP will be higher due to the elimination of the shift. But the league average BABIP already includes an 8 point increase in BABIP over 2022, and therefore already accounts for the shift rule impact. I expect the Astros’ pitching BABIP to continue to regress downward.

When the stats are broken down between starters and bullpen, the starting rotation is ranked fourth best in ERA (3.22). But the bullpen (ranked 14th best in ERA) is affected by even worse BABIP luck at .309, which is the 10th highest BABIP in the majors. So, even though the bullpen results have been worse than the rotation, we probably can look forward to regression in the direction of the .288 league bullpen BABIP.

The Astros’ pitchers have primarily suffered damage from batted balls hit into the air. Three of the five members of the rotation lean toward allowing balls in the air. The batting lines for fly balls and line drives against Astros’ pitching is shown below.

(BA, OBP, SLG, OPS)

Fly balls .201, .200, .604, .804

Line drives .706, .699, .990, 1.698

42% of the balls hit in the air have been line drives (which is slightly higher than 2022). The SLG and OPS for fly balls primarily reflect HRs. The batting line and OPS for line drives is considerably higher than 2022. The OPS for line drives allowed by the Astros is 12% higher than the league average. My guess is that we will some regression, which leads to more “normal” line drive batting lines. But, given the number of airball pitchers on the staff, we should probably watch the line drive results in the future to see if a trend develops. Also, the air ball batting lines will be influenced by outfield defense. Last year the Astros enjoyed the best outfield defense in baseball (according to DRS). Because defensive metrics require larger sample sizes, it is too early to evaluate the outfield defense in 2023. But so far, DRS indicates that the Astros outfield defense has been, at best, only slightly above average.

Stuff+ Rankings

Fangraphs’ leaderboards now contains a new pitching metric, Stuff+, which is based on the physical characteristics of pitches (such velocity, movement, and location). There is evidence that the overall Stuff+ rating predicts future ERA performance. In addition, Stuff+ also provides information on a pitch-type basis. In theory, Stuff+ should have greater statistical meaning in smaller sample sizes than are required for more traditional pitching stats.

I think there is value in examining team rankings of Stuff+ in order to evaluate the relative position of a team’s overall pitching stuff. I think this may provide a better point of comparison for examining the current Stuff+ with the previous season Stuff+.

• The Astros’ overall pitching staff is ranked 3d in overall Stuff+ this year. This indicates that the Astros’ pitching staff continues to be a superior group in terms of pitching stuff. However, the Astros’ ranked 1st in overall Stuff+ in 2022. So, relative to other teams, the Astros’ Stuff+ position isn’t quite as good as last year.
• The relative position of the starting pitchers’ Stuff+ has declined notably. The Astros’ starters are ranked 12th in Stuff+, which is not terrible—but it’s also a significant decrease from 2022. The Astros’ starters were ranked 2d in Stuff+ in 2022. Of course, the loss of Verlander, who put up a terrific Stuff+ number, is an important factor in the decline. The somewhat tepid Stuff+ numbers for the Astros’ rotation validate the “eye test” observation that several Astros’ starters have experienced problems such as lower velocity, insufficient pitch movement, and location issues. Despite the “stuff” problems, the Astros’ starters as a group has maintained a good ERA.
• The Astros’ relievers are No. 1 in Stuff+. This is the same ranking as 2022. The bodes well for the bullpen returning to its previous prominence in shutting down opposing offenses. It also provides credence to the notion that the bullpen’s contribution to losses in the early going is due to bad luck.

The Astros’ staff rankings for Stuff+ by type of pitch are compared to 2022:

2023 Stuff+ Ranking / (2022 Stuff+ Ranking)

4 seam Fastball 8th (3d)

Sinker 14th (6th)

Cutter 2d (2d)

Splitter 5th (7th)

Slider 8th (1st)

Curve 5th (2d)

Change Up 19th (2d)

Knuckle Curve 11th (9th)

I’m not sure that there is a big takeaway from the pitch-by-pitch rankings. For the most part, this is really for general interest as opposed to reaching any diagnostic conclusions. The change-up isn’t thrown a lot, so I’m not sure the decline from 2022 means anything. The slippage in rankings for the fastball, sinker, and slider is something to watch because Astros’ pitchers rely so much on those offerings. But, again, given the sample size, I wouldn’t put too much weight on the ranking. It is mildly interesting that the Astros’ pitchers continue to rely on extensive use of the cutter because they throw very good cut fastballs.

What are your thoughts?

(Data through 4/17/23)