Platoons: how MLB lineups change against left-handed pitchers
One of the most visible drivers of day-to-day lineup changes is the opposing starter's throwing hand. In 2025 the average MLB lineup had 3.6 left-handed hitters against right-handed starters but only 2.1 against left-handers.
The platoon idea
Hitters tend to do better against pitchers who throw with the opposite hand: left-handed hitters against right-handed pitchers, and right-handed hitters against left-handers. In The Book: Playing the Percentages in Baseball (Tango, Lichtman and Dolphin, 2007), the average platoon split for left-handed hitters was about 25 points of wOBA, and the authors warn that a single season's split for one player is heavily affected by chance. A "platoon" is the practice of splitting a position between two players, typically starting a left-handed hitter against right-handed pitchers and a right-handed hitter against left-handers.
Switch-hitters can bat from the opposite side against either kind of pitcher, and in 2025 their number in the lineup barely changed (1.01 vs RHP, 0.99 vs LHP). Because most starting pitchers are right-handed, left-handed hitters get most of their starts against them, and a team's lineup against a left-hander often looks noticeably different.
2025 in numbers
| Opposing starter | Team-games | Left-handed hitters | Right-handed hitters | Switch-hitters |
|---|---|---|---|---|
| Right-handed | 3,583 | 3.62 | 4.38 | 1.01 |
| Left-handed | 1,277 | 2.09 | 5.91 | 0.99 |
Teams faced a left-handed starter in 26.3% of games. In those games they started about one and a half fewer left-handed hitters, replaced almost one for one by right-handed hitters, while the number of switch-hitters barely moved. Clubs differed a lot: the average number of left-handed hitters a club started against right-handers ranged from 1.0 to 4.9, and against left-handers from 0.6 to 3.6. (The figures in the table pool all team-games; the average of the 30 clubs' own averages is slightly different, 3.6 and 2.0, because clubs faced different numbers of left-handed starters.)
Why the late innings changed
Platoon matchups also shape the bullpen. Since 2020 the rules have required a pitcher to face at least three batters or finish the half-inning, unless he is injured or ill, which limits the use of a reliever brought in to face a single left-handed hitter.
What it means for projections
- The probable opposing starter's hand is one of the first things our projections use. If the probable pitcher changes from a right-hander to a left-hander, several players' start probabilities can move at once.
- Platoon players are the ones whose start probability depends most on that hand. Our planned team pages will list them.
- Our first baseline already split its history by the opposing starter's hand; see methodology.
Sources: Official Baseball Rules (three-batter minimum, in effect since 2020); T. Tango, M. Lichtman, A. Dolphin, The Book: Playing the Percentages in Baseball (2007), ch. 6. Figures: our own calculations. The information used here was obtained free of charge from and is copyrighted by Retrosheet. Interested parties may contact Retrosheet at "www.retrosheet.org".