It’s no secret that the Astros are entering the 2025 season with a paucity of LHBs. We look at the platoon splits of the rival Mariners’ and Rangers’ rotations.
Strategies based on platoon splits are almost as old as modern era baseball. The match up favors the pitcher when the batter and pitcher are same handed.
Over the last couple of years, the Astros’ lineup had among the fewest LHBs in the MLB. Then this off-season, the Astros traded one of their two regular LHBs (Kyle Tucker). That left Yordan Alvarez as the only regular LHB in the lineup. Throughout the off-season, we wondered if the Astros would acquire another LHB. The Astros looked at some additional LHB options in the spring but the Astros will head to the regular season with only Yordan Alvarez as the regular LHB.
Taylor Trammel, a LHB outfielder, suffered an injury early in spring camp and was sidelined during spring training. LHBs Ben Gamel, Jon Singleton, and Luis Guillorme were cut late in spring training. At this point, Cooper Hummel, a switch hitter, is still in the running for a bench / PH position. Back up catcher Victor Caratini is also a switch hitter, though the LHB isn’t necessarily his dominant side.
Earlier this year, I utilized Steamer projections to estimate the 2025 platoon differential for the Astros offense. According to my calculation at the time, the Astros’ platoon differential is projected to be 41 points of OPS, which is relatively large. For example, in 2024 the average platoon differential for MLB teams was 11 points of OPS. This means the team offense is advantaged vs. LHPs and disadvantaged vs. RHPs. Given that more pitchers are right handed, the composition of the team’s lineup isn’t optimal for maximizing the offense.
It will be interesting to see how opposing teams react to the Astros’ RH dominant offense. To the extent it’s feasible, teams may manipulate their rotation schedules to ensure that the Astros face RHPs with dominant righty splits as much as possible. During Monday’s game, the television broadcast team said the Mets had arranged their opening series rotation schedule against the Astros to exclude LH starting pitchers.
Reportedly the Rangers signed the LH slugger Joc Pederson in part due to the RH heavy starting rotations of the Astros and Mariners. With that in mind, we will examine the projected platoon splits for the Mariner’s and Ranger’s starting rotations in order to evaluate how it might affect match ups with the Astros offense.
Steamer projections include a platoon splits feature for pitchers I compiled the projected RHB and LHB wRC+ split for pitchers in the probable five man rotations. For the Rangers, I excluded the injured pitchers (Gray and Bradford) and added Rocker and Leiter to the rotaton.
The projected 2025 splits for wRC+ are shown below.
Steamer Projections
- As expected, both rotations are tougher on RHBs than LHBs. The average wRC+ for the two rotations: Texas vs. RHB 92.2, Texas vs. LHB 102.4; Seattle vs. RHB 86.4, Seattle vs. LHB 97.6. The difference in RH and LH splits is approximately 10 points of wRC+ for both teams.
- The Rangers have an incentive to maximize the number of times deGrom and Eovaldi face the Astros, given that they allow wRC+ of 59 and 94 against RHBs. deGrom’s wRC+ of 59 when facing RHPs is insanely low, meaning that he is expected to be very tough on righthanded batters. The young pitcher Kumar Rocker has a surprisingly low projection against RHBs. Patrick Corbin isn’t shown, because I assume he will be used as depth. But he is a LHP with very poor projected splits against RHBs (124 wRC+). My guess is that Texas will avoid matching up Corbin with the Astros’ lineup, if they can.
- All of the Mariners’ starting rotation allows quite low wRC+ against RHPs. Castillo is projected to have a huge difference in splits (20 points), as evidenced by a 82 wRC+ vs. RHB and 102 wRC+ vs. LHB. Gilbert, Miller, and Kirby are also exceptionally tough on RHBs (wRC+ of 81 – 83). The Seattle rotation is very good, but lefthanded bats have a better chance to make hay off of Miller (103), Castillo (102), and Woo (102). The Astros will hope that Alvarez is prepared to take on those three starting pitchers.
Now let’s put the projections away and find out what happens in the regular season.