Starters vs Bullpens: How Innings Are Split in Today's MLB

In 2019 MLB starters averaged 15.5 outs per start. In 2022 it was 15.6, in 2024 15.7 and in 2026 about 15.2. That is five innings — a little over half the game. The rest belongs to the bullpen, so a projection built only on the starter is missing almost half of the pitching.

Quality times quantity

BullpenEdge weights the opposing starter's projected rates by his expected share of the game, and the bullpen's by the rest. An ace expected to go six-plus innings dominates the calculation; a starter on a short leash or coming off the injured list hands more of the game to the relievers. A pitcher's expected innings come from his recent starts, so an opener used for one inning gets a tiny share automatically.

The first five innings

Because the starter usually covers about five innings, the first half of a game is where the starting matchup matters most, and the late innings are where bullpen depth and rest take over. The Game Analyzer splits each team's expected runs into 'opposing starter' and 'opposing bullpen' so you can see which half of the game is driving the projection.

Bullpen games

When a team announces no starter, the projection uses a generic short start until one is named, and it is updated on each run of the pipeline. That is one reason a projection can move during the day.