The Astros Have Turned Their Season Around Thanks To Their Pitching

Thanks to contributions from a wide number of both starters and relievers, the Astros lead the majors in ERA over their last 81 games. As a result, they also lead the majors in wins since May 8.

Who has been the best team in baseball over the last 5 games? That’s easy. As you know the Astros have won the last 5 straight, winning the final two in Arlington before sweeping the Red Sox in Fenway Park over the weekend.

Who has been the best team in baseball over the last 81 games? That’s harder. One might think it’s the Orioles or Yankees, at the top of the AL East, or the Phillies who have the NL’s best overall record.

But the answer is also the Houston Astros. It’s okay if you did not know that before this post, because I didn’t know it until I saw this tweet earlier today from friend of the Substack Tony Adams. The Astros are 1.5 games up on the Diamondbacks for the best record in baseball since May 8. They are 5 games up on the Yankees, Orioles, and Guardians for the best record in the AL.

And as Tony points out, the Astros have done this primarily through their run prevention. Over the last 81 games, they have allowed only 295 runs, which is 3.6 runs per game.

I think this will surprise many Astros fans for a simple reason—there has been a great deal of stress on the starting rotation due to the injuries to Cristian Javier and Justin Verlander and the slow recoveries of Luis Garcia and Lance McCullers from their arm surgeries last season. The bullpen has had some spectacular blowups which have been quite memorable.

But the stats are the stats. They show you what actually happened. You can see that in the chart below, which shows the Astros pitching stats since May 8. I also included the Astros rank among the 30 teams of MLB so you can see how good (or bad in a couple of cases) the Astros hurlers are doing.

Overall, they are doing quite well. Unsurprisingly for the team that has given up the fewest runs in the league during this period, the Astros lead MLB in ERA since May 8. They also lead the league in lowest batting average allowed at .220.

One secret to the success of the Astros pitchers—they are striking lots of batters out. They have struck out over a quarter of the batters they have faced—which is second best in the majors.

There are some indications that run prevention abilities of the Astros pitchers has been affected by some good fortune. The staff’s batting average on balls in play (BABIP) is .272, which is second best in baseball. Over time, this number tends to move toward the league average of .289. That helps explain why the Astros FIP of 4.10 is much higher than the team’s ERA. It’s worth noting that the team’s xFIP, which uses a team’s expected, rather than actual home run rate, is lower than the FIP. So some of the good luck on batted balls in play is taken away from poor luck on home runs.

The Astros also have an LOB%—which measures the share of baserunners who are left on base—of 78.7% during this time period. Thanks to a combination of strikeouts and keeping balls in play from becoming hits, the Astros allow relatively few baserunners to score.

The table shows two clear areas of weakness for the Astros pitching staff. The team has the 27th highest walk rate in the majors at 9.0%. This is not good, but the high strikeout rates are helping to mute the effect of these walks.

Astros pitchers also tend to give up a high share of home runs per fly ball. Their 13.2% HR/FB rate is 23rd highest in the majors.

These are two worrisome stats. But they do not cloud an overall sunny picture—the Astros are keeping runs off the board and, as a result, they are winning baseball games.

Who is contributing to the Astros excellent pitching over the last 81 games? The answer is lots of different players. It’s a widescale effort.

The table below shows the innings pitched and ERA since May 8 for a wide number of Astros pitchers. The starting pitchers are on the left hand side and the relievers are on the right.

The Astros starting pitchers all have ERAs below 3.50 over the last 81 games with the exception of Spencer Arrighetti. And Arrighetti has been improving as he has adjusted to major league hitters—c.f. his start on Saturday in Boston. Hunter Brown, who was in danger of being sent down early in the season, has turned it around and performed like an ace.

In the bullpen, one can again see the depth of the Astros options. Bryan Abreu, Ryan Pressly, and Josh Hader look like the studs we expected to see, and Tayler Scott has been a revelation this season. But it is worth noting the quality work the Astros are getting from less heralded bullpen options such as Shawn Dubin and Bryan King. I kept Rafael Montero on the chart for comic relief.

Overall, the starting pitching has had a 3.64 ERA since May 8, good for 2nd best in the majors. The bullpen’s ERA is 3.15, which is 5th best.

It is also worth going back to the Tony Adams tweet and note that between the 50 wins and 31 losses, the Astros have played 81 games. since May 8. That’s half of a season. Anybody can have a hot week or two. The Astros pitchers have had a hot half a season.

Thus, this isn’t a short sample fluke. It’s the sign that this team can pitch very well. And it’s why this team has won more over the last 81 games than any team in the majors.