Astros are rolling with a bullpen day on Tuesday

For the first time this season, the Astros will not be using a starting pitcher from their Opening Day roster. In today’s baseball, that streak is simply impressive.

Lance McCullers strained a muscle in right forearm swinging a bat on August 4th at Dodger Stadium. In turn, he was placed on the DL the following day with a projected return scheduled for some time in September. We’ve all known for a while that the Astros‘ streak of using the same five starting pitchers all season would eventually end. But thanks to the scheduled off-days throughout August, Houston was able to use only four starting pitchers during the last couple of weeks. Basically, the Astros have had the flexibility to simply skip McCullers’ turn through the rotation.

There isn’t anything particularly noteworthy about this development besides the fact that Houston was the only team all season to use the same five starting pitchers. The streak will officially end on Tuesday as the Astros will trot out their sixth starting pitcher of the season. For comparison sake, Houston used eleven starting pitchers last season. In lieu of a traditional starter though, manager AJ Hinch has revealed that the Astros will have a bullpen day at Safeco Park on Tuesday. Here is a quote saying as much from Hinch courtesy of the Houston Chronicle’s Chandler Rome.

"“Those guys are all viable options,” Hinch said Monday. “It’s a bullpen day, and as I told Servais, I’m not going to hide anything — we all know what those have turned into nowadays."

The unorthodox strategy of a “bullpen day” has become a hot topic of discussion across baseball this season. Thanks in part to the Rays’ well-known “bullpen day” usage, the idea has gained traction from other teams. The Padres, for example, employed a “bullpen day” against the Braves in mid-June. I would know because I was actually at the game.

The idea of a “bullpen game” does make sense, especially when you’d consider the potency of opposing lineups in the first inning.

Table 1. MLB wRC+ By Inning

1st: 106 wRC+
2nd: 90 wRC+
3rd: 92 wRC+
4th: 101 wRC+
5th: 103 wRC+
6th: 102 wRC+
7th: 94 wRC+
8th: 93 wRC+
9th: 88 wRC+
Extras: 97 wRC+

Relievers are typically more effective in shorter spurts than starting pitchers. It is just nature of the roles. So why not have one of your top relievers go against the opposing lineup’s best hitters in the first inning? As the numbers above indicate, offensive production dives in the second and third innings before rebounding in the middle innings. The middle innings is usually around the time when the typical starting pitcher goes through the lineup a second or third time. Pitch count also becomes an issue. Offensive production then dips as you head into the later innings, and that is when the bullpen historically enters the fray.

Hinch noted in Rome’s article that he will likely appoint either Will Harris, Brad Peacock, or Joe Smith as the “opener” for Tuesday’s game. In a later article from Rome, the Astros made the decision to go with Peacock. The decision makes sense as Collin McHugh, Tony Sipp, and Ryan Pressly pitched on Monday night, so it is plausible to understand why they weren’t named as potential options. Keeping with the conventional thinking, Roberto Osuna and Hector Rondon will be options for the later innings. Personally, I would’ve strongly considered the possibility of using one of those two relievers in the first inning. Look at the opposing lineups again in the first inning.

Of the three options listed by Hinch, I would’ve probably rolled with Smith as the “opener” instead of Peacock. While he doesn’t have experience starting a game, Smith has held opposing hitters to a .264 wOBA with the bases empty. Opposing hitters against Peacock, by comparison, have a .304 wOBA with the bases empty. While situations with the bases empty doesn’t dictate the entire decision, each game starts with the bases empty. Smith (.159 wOBA) has also arguably been the better pitcher over Peacock (.304 wOBA) in the second half.

Peacock, in my opinion, would’ve been a logical choice in the second and third innings when the opposing lineup usually doesn’t have its best hitters ready to bat. If he pitches effectively, he could complete two-to-three innings. But I can understand why the Astros went with Peacock to “open” as he has experience starting a game, and the team surely has more data at its disposal to justify their reasoning.

I am quite curious to see how the “bullpen day” goes for the Astros. The challenge will be to bridge together nine innings of effective pitching. But Houston does have the pitchers to pull this idea off. Let’s just hope no one has an off-day.