One of the most bizarre facts about the Astros in 2023 was that they were 39-42 at home (tied for 19th best) and 51-30 on the road (3rd best).
The universal question has been "Why are the Astros so bad at home?"
One of my Patreon supporters asked me to go through this rabbit hole and solve this riddle for the Astros fan base. This is a perfect topic for us at LarryTheGM.com. This is why you have the LarryTheGM.com website. PLEASE support the work here. There are two opportunities for you to support the
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Today, let's focus on how the pitching caused the Astros to struggle at home in 2023 relative to the team on the road. This is a two-part series. We previously covered the hitting side of the home struggles here.
Hold on readers. This is going to be a data avalanche.
Let's start high level with some basic data.
Home Data
The Astros gave up 4.70 runs/game at home. They have a slightly positive wOBA gap at home meaning the wOBA was higher than the xwOBA. This means that based on the contact the batters made, the pitchers SHOULD have given up less hits. This unlucky reality accounts for about 0.19 runs/ game. Part of that difference is explained by a home BABIP of 0.308 which is above the league home average of 0.299. Overall, the models I have built would project that the Astros SHOULD have given up 4.57 runs per game - slightly below the 4.70 runs they did give up. They SHOULD have been slightly better at home.
Away Data
The data for the Astros on the road is far more interesting. The Astros allowed 3.91 runs per game. The team had a large negative wOBA gap away meaning the wOBA was significantly smaller than the xwOBA. This means that based on the contact the batters made, the pitchers SHOULD have given up more hits. This significantly lucky reality accounts for about 0.57 runs/ game. THAT is a big gap. Part of that difference is explained by an away BABIP of just 0.273 which is way below the league road average of 0.295. Overall, the models I have built would project that the Astros SHOULD have given up 4.83 runs per game. In reality, they gave up 3.91. This is a MASSIVELY lucky result.
The FIP of 4.41 away reflects what should of happen. Notice the away FIP is HIGHER than the home FIP.
They were unlucky at home and VERY lucky on the road.
For the rest of this exercise, I am going to focus on how each pitcher pitched at home vs. on the road. Were they part of this massively lucky 0.92 run gap away from home?
This next table is massive. Focus on the comments I repeat below. Purple shaded cells favor road performance. Green cells favor home performance.
If you can't read that focus on these comments.
Focusing on JUST FIP and ERA highlights again what I said earlier.
The home ERA was 0.63 worse than the road ERA, BUT the home FIP was 0.20 better that the road FIP.
As shown above the pitchers leaving had a completely unsustainable 2.45 ERA on the road. Their FIP as a group (3.94) was almost 1.5 higher than that ERA.
Many of the Astros pitchers had BABIP issues at home (Blanco, Brown, Montero, Martinez) or BABIP luck away (Blanco, Maton, Nevis).
Many of the Astros pitchers had wOBA gaps fueling the good road vs. home performance too.
I was curious did the Astros as a team have a significantly different pitch mix at home vs. away.
The Astros 4-seam fastballs were down a little away but more effective away. This looks like yet another BABIP issue.
The Astros used less sliders at home vs. away. The sliders were more effective away too.
The Astros used a slightly more curveballs at home and they were effective at home and on the road.
Another interesting phenomenon was that splitters were GREAT on the road and not as good at home. The exit velocity difference of 4.6 mph is curious.
Perhaps the good news is that much like the Astros hitting at home vs. road, the differences for the Astros pitching are coming down to luck again. The Astros road BABIP of 0.273 and 3.62 ERA vs. a 4.41 FIP are not sustainable.
The bad news is this. If I consolidate the actual runs produced data by the offense we discussed previously and the runs given up by the pitching, we get one view of the performance. However, if I consolidate the same data for the PROJECTED runs, it shows the net effect of luck.
The Astros won
39 games at home
51 games on the road.
Based on their actual runs produced, the Astros SHOULD have won (per the Pythagorean runs theory)
39 games at home
54 games on the road
Based on the PROJECTED runs they SHOULD have scored (via xwOBA model), the Astros should have won
43 games at home
43 games on the road
Yes, the Astros should have been better at home. They SHOULD have been significantly worse on the road. In fact, if the Astros had won the games their performances project to without luck, the team would have won 86 games in 2023. That means they would have missed the postseason.
Altogether, I guess we as Astros fans should be happy the team was so lucky on the road vs. unlucky at home.
Let's hope they are lucky AND good wherever they play in 2024.