Starters now record about 15 outs a game (starters vs bullpens), which leaves roughly 12 outs a night to the relievers. Depth charts and broadcasts label those relievers with short tags: CL, SU, MRP, LRP. This guide explains each role, how managers actually use them, and how the save, hold and blown-save stats are scored, with examples you can check against the rules.
The roster frame
An MLB active roster has 26 players, and since 2022 no more than 13 of them can be pitchers (14 when rosters expand to 28 in September). With five starters, that leaves about eight relievers. The three-batter minimum, in force since 2020, also shapes usage: a pitcher who enters must face at least three batters or finish the half-inning, unless he is hurt. That rule ended the one-batter left-handed specialist (the "LOOGY") and pushed teams toward relievers who can get both lefties and righties out.
The roles, from the ninth inning back
- Closer (CL): usually the best reliever, saved for the ninth inning of close games. Teams like a closer who strikes out a lot of hitters, because a strikeout cannot turn into a bloop hit or an error.
- Setup man (SU): pitches the eighth, or the most dangerous part of the lineup in the seventh or eighth. On many teams the setup man is as good as the closer and is used in the highest-leverage spot whatever the inning.
- MRP (middle relief pitcher): covers the sixth and seventh, often bridging from a starter who has gone five. Middle relievers are a mix of rising arms and veterans, and their quality is where bullpens differ most.
- LRP (long relief pitcher): can throw two to four innings, so he is used when the starter leaves early, in blowouts, or in extra innings. Long men are often former starters and are the first to make spot starts.
- Opener: a reliever who starts the game and gets the first three to six outs, usually against the top of the order, before a "bulk" pitcher takes over. The Tampa Bay Rays popularized it in 2018.
- Mop-up: whoever pitches when the game is out of hand, saving the important arms for tomorrow.
Leverage: why roles bend
Leverage index (LI) measures how much the game outcome is riding on a plate appearance, with 1.0 as average. FanGraphs treats an LI under 0.85 as low leverage and above 2.0 as high (FanGraphs: leverage index). A runner on third with one out in a tie game in the eighth is far more important than a clean ninth with a three-run lead, which is why analytically minded managers will bring the best reliever into the eighth and leave the ninth to someone else. Roles still exist because pitchers like knowing when they will pitch, but the best teams bend them for leverage.
How a save is scored
Under the official scoring rules (MLB glossary: save), a pitcher earns a save when he finishes a game his team wins, is not the winning pitcher, records at least one out, and meets one of three conditions:
- He enters with a lead of no more than three runs and pitches at least one inning.
- He enters with the tying run on base, at bat or on deck.
- He pitches at least three innings, whatever the lead.
Worked examples: leading 5–2 to start the ninth, the closer gets three outs. Lead of three, one full inning: save. Leading 6–2 to start the ninth with the bases empty, he gets three outs: no save, because the lead is four and the tying run is not on base, at bat or on deck. But if that 6–2 lead becomes bases loaded with one out and a new reliever comes in, the batter at the plate is the tying run, so that reliever is in a save situation and earns a save by getting the last two outs. And a long man who throws the last three innings of an 8–2 win gets a save under the third condition.
Holds and blown saves
- Save opportunity (SVO): any appearance that meets the save conditions when the pitcher enters. Save percentage = saves ÷ save opportunities.
- Blown save (BS): the pitcher enters in a save situation and gives up the tying run (or the lead). He can still be the winning pitcher if his team scores again, which is how a "vulture win" happens.
- Hold (HLD): the pitcher enters in a save situation, records at least one out and leaves with the lead intact, without finishing the game. MLB tracks holds, but they are not one of the stats defined in the Official Baseball Rules (MLB glossary: hold).
Example inning by inning: starting pitcher leaves after six with a 3–1 lead. The seventh-inning reliever throws a scoreless inning and gets a hold. The eighth-inning reliever allows one run but leaves leading 3–2: also a hold. The closer throws a scoreless ninth: save. If instead the closer had allowed the tying run and his team had won it in the bottom of the ninth, he would be charged with a blown save and credited with the win.
Reading a bullpen's numbers
- Saves measure opportunity as much as skill: a good closer on a bad team gets few chances. Strikeout and walk rates, and the ERA estimators in FIP, xFIP and xERA explained, tell you more about how good a reliever is.
- Reliever samples are small. Sixty innings is a full season for a reliever and is about 250 batters faced, so a reliever's ERA can swing by a run or more on a handful of plays. Lean on multi-year rates, as in the Marcel method.
- Availability changes every day. A closer who threw 25 pitches yesterday or pitched the last two days is usually down; see bullpen fatigue and availability for the rules BullpenEdge applies.
Every game page on BullpenEdge splits the projection into the opposing starter and the opposing bullpen, and every team page shows the last three days of reliever pitch counts, so you can see which roles are covered on a given night.