Closers: Often the best relief pitcher on the team, a closer usually enters the game in the ninth inning with a narrow lead to record the save by pitching the final few outs. Closers throw an average of 1-2 innings per outing. Some elite closers, such as Mariano Rivera or Craig Kimbrel, earned multiple all-star selections and became known as lights-out closers extremely difficult to hit against in pressure situations.
Set-up pitchers/middle relievers: Pitchers who typically enter the game in the 6th through 8th innings to bridge the gap between the starting pitcher and the closer. They earn holds (like a win) instead of saves. They generally have success against both righties and lefties. Good setup pitchers lengthen the bullpen and provide insurance for when the starter is unable to finish deep into games.
Left-handed specialists: These pitchers enter the game specifically to counter left-handed batters late in the game. They focus on just getting out lefties through their pitching style and stuff. A bad matchup against a righty can result in their quick removal. Examples include names like Jerry Blevins, Wade Davis, and Tyler Matzek who thrived in their specialist roles.
Long relievers/mop-up men: Relief pitchers used when a starting pitcher fails to get through the minimum number of innings. These pitchers are expected to eat up innings but may give up runs since they face the heart of the opposing lineup. Teams instead prefer to use functional relievers in multiple innings to preserve the bullpen for closer situations.
Opener: An innovative recent strategy where a relief pitcher starts the game and typically faces 2-3 hitters before handing it over to the following pitcher in more of a traditional starting role. Openers allow teams to gameplan matchups better. Former Rays reliever, Ryan Yarbrough, became one of the first prominent “openers”.
Because of their versatility and varied roles, relief pitchers typically do not pitch as many innings in a given season as starters. As such, relief pitcher baseball cards often note their specialty type using the designation “RP” to provide context for their career stats and value on the trading/collecting market. The cards may also include stats tailored to relief pitchers like games finished, holds, wins, blown saves, ERA as a reliever, etc. This additional information helps show the important, nuanced roles that relief pitchers play in winning ballgames. While not traditional starters, relief pitchers remain valued commodities for championship teams depending on how they perform in their specialized bullpen function. Their cards recognize the specialty skills they bring which are different than starting pitchers.