The Astros will have vacancies in four of the 2023 bullpen slots. Hector Neris, Phil Maton, and Ryne Stanek, who are free agents in 2024, pitched 184 innings out of the bullpen in 2023. The fourth vacancy arises with the news that Kendall Graveman will not be available in 2024 due to surgery. The Astros now face the task of replacing those pitchers either externally (trade or free agency) or internally (promotion of minor league pitchers).
Relief pitchers are notoriously volatile, meaning their performance can swing back and forth between seasons—which increases the difficulty of constructing a bullpen.