What Does LRP and MRP Mean in Baseball?

What Does LRP and MRP Mean in Baseball?

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As modern baseball evolves so, too, does its vernacular. Perhaps nowhere in the game has the language changed more than in the bullpen. Historically almost an afterthought, today’s relief pitchers can be part of serious strategic game play. They even get new specialized acronyms now.

For instance in baseball, LRP and MRP stand for Long Relief Pitcher (LRP), and Middle Relief Pitcher (MRP). Long relievers are placed in games sooner than middle relievers, in the early- to middle innings. Middle relief pitchers are usually deployed in the 6th and 7th innings of games.”

Longtime baseball fans are sure to understand that the old acronym RP means relief pitcher. Now they have LRP and MRP, which are linked with the SU and CL: for set-up (pitcher) and closer. Altogether these acronyms indicate just how far relief pitching has progressed the past third of a century.

Not only are pitchers assigned to the bullpen ~ where pitchers expected to enter later in games sit awaiting call-up to the mound, or to warm up ~ but they also might be specialized as to precisely when they will be inserted into the action. Here’s some insight.

Difference Between LRP and MRP in Baseball

Usage of LRP and MRP is actually not necessarily common on baseball fields. These acronyms surfaced mainly due to technology: for use in video games, or fantasy baseball.

The terms long relief and middle relief have been around for a very long time. It’s just that now in certain formats (e.g. video games) a manager needs to know up-front the types of relief pitcher, to help with game strategy and decisions.

The difference between LRP and MRP is that long relief pitchers usually enter a game to replace a starting pitcher, and then go several innings. On the other hand, it’s rare for middle relief pitchers to go more than a single inning. The long reliever usually enters in the first 5 innings; the middle relievers come in after that, most typically the 6th and 7th innings (because set-up pitchers take inning 8 and closers take inning 9).

Typical Scenarios

  • Starting pitcher struggles early in a game. This is exactly why teams might designate a long-reliever. If a starter gets bombed or hurt in the 1st inning, it puts stress on a bullpen to work all the remaining innings of a game. Long-relievers are usually starters who did not crack the team’s rotation, but their arms are used to throwing multiple innings. They are better suited to take on multiple innings.
  • Early blowout. If one team falls way behind in the early innings, they might go with a long-reliever with hopes he will last many innings, maybe even the entire game. The reason: if you’re going to lose no matter what, why “waste” the energy in your relief pitcher’s arms?
  • From fireman to closer. Baseball has long had “saves” and “firemen,” the pitcher brought in to stop rallies or end games. What changed in the late 1980s is the specialized “closer” ~ who throws usually no more than an inning at the very end to win games. Old-time firemen pitchers might have been brought in at any time during a game to douse a rally; and then keep pitching more than an inning. The closer mostly enters games in the 9th inning only.
  • Specialized BP roles. Actually, BP is rarely used to denote bullpen, because it’s long been associated with batting practice. Still, a Major League Baseball team might carry 7 or 8 relief pitchers on a roster, and each is expected or planned to play a specific role. Sometimes, as noted above, these pitchers will have a pretty good idea when they might enter a game. Others, like a “left-hand specialist” might be brought in to throw only to 1 or 2 batters (who will be left-handed hitters).

History of LRP, MRP, and Relief Pitchers in General

Relief pitchers are any hurler who enters a game but not at the very beginning. That’s the starting pitcher. Relief pitchers have been around since the invention of baseball, since pitchers are human and as such none are perfect all the time.

Teams and managers learned quickly that pitchers tire, get hurt, or just don’t have good movement on their pitches so the other team is hitting him hard. Sometimes the starting pitcher just has bad luck and a manager wants him out of there.

In those cases, the pitcher is “relieved.” In early baseball the relievers were basically pitchers not good enough to start. Starters were expected to finish games, and only if problems surface aware relievers called upon.

Then with free agency starting in the 1970s, plus a slow implementation of advanced statistics into baseball strategy, that group of guys out in the bullpen became specialized.

Here, we’ll try to explain each role by using historical MLB players.

Original Relief Pitchers

Those unfamiliar with baseball won’t know that baseball’s starting pitchers can’t play for several days after a start, usually 4 or 5 days. It’s to rest their arm after tossing a baseball 100 or more times overhand in a single game.

Additionally, into the 1960s, starting pitchers were expected to finish the games they initiated on the mound.

In the very old days “relief” pitchers were most often starting pitchers on their days off taking an inning or 2 to stay sharp or work on things.

It began to shift slowly starting after World War II. Some teams began tagging a single relief pitcher for end-of-game or high-leverage game situations. Early “firemen” often featured an odd pitch to get outs, like Hoyt Wilhelm’s knuckleball. Since relievers pitch fewer innings than starters and therefore more games, Wilhelm in his career broke the all-time record for games pitched.

Relief specialists like Hoyt and forkballer Elroy Face stuck around into the 1960s, and then when Major League Baseball lowered the pitcher’s mound to create more offense, teams countered with more specialty relievers to put out “fires.”


Among early firemen was Sparky Lyle, who was first assigned to douse offensive fires for the Boston Red Sox, but who made the role more known with his game-closing heroics with the New York Yankees.

Another notable fireman was Mike Marshall of the Los Angeles Dodgers, who set the record for 106 games pitched in 1974; and John Hiller of the Detroit Tigers, who manager Billy Martin began using as a weapon in any inning as needed starting in 1973.


Later in the 1970s managers began tapping a single pitcher, usually a very hard-thrower, or someone who dominates with an unhittable pitch, to throw at the very end of games to seal victories. Goose Gossage and Bruce Sutter come to mind. However early closers still often pitched more than an inning.

It wasn’t until Oakland Athletics manager Tony LaRussa made future Hall of Famer Dennis Eckersley into a 1-inning pitcher that today’s role of “closer” surfaced.

‘Closer Era’ Ending?

While closers remain in the MLB through the 2021 season, not every team identifies a single player in that role. Relief pitching began to evolve in the mid-teens of the 21st century, with managers choosing to bring in their very best arm from the bullpen when the game situation called for it.

A great example is the 2016 Cleveland Indians, where manager Terry Francona rode lefty Andrew Miller to the World Series. Other teams began to follow, sometimes bringing in their best reliever in the 8th inning instead of at the very end.

In recent years teams even invented what is known as an “opener” ~ a player usually a relief pitcher chosen to begin the game, but not expected to last long. These games are called “opener” or “bullpen” games because the manager opted not to begin with a starter, but to use a strategy to bring in the best pitcher possible for any troubling situation.

The LRP and MRP to the Forefront

Which brings us to LRP and MRP. The Long Reliever and Middle Reliever designations have been around for many years, invented by managers so those pitchers (and coaches) understand expected roles. So many types of relief pitchers surfaced in the 1980s and 1990s, people on the field, and even game announcers, needed ways to differentiate between them.

But not everyone used the acronyms LRP and MRP. Those were brought to the forefront by baseball-based video games and fantasy sports leagues.

In fantasy baseball, for instance, a league could choose to make one of its roster spots specific to a middle reliever. Maybe that league counts appearances or holds as a statistical category, and the best middle relievers carry value. Hence, those leagues might limit a roster spot to only MRPs.

Same with video games: designers running out of things to make their game as realistic as possible might get down to identifying players as LRPs, etc. Games might have caps on how long a particular position can throw, e.g. only 1 inning for a closer before he must be removed, or no more than 2 innings for a set-up man.

It just makes it more challenging for the participating players (the video game players that is) to work harder to “manage” their team.

Final Words on Baseball’s LRP and MRP

The simple way to differentiate a long-relief pitcher and middle-relief pitcher in baseball is, the long reliever is expected to stay in the game longer. That is, managers hope the LRP will end more innings. The MRP, on the other hand, mostly throws for an inning or less.

Finally, the long-reliever almost always follows the starting pitcher. Middle relievers, however, usually come in to replace another reliever. This usually occurs in the 6th or 7th innings, before the set-up man takes the 8th, and the closer comes in for the 9th.

See Also:
Why do Pitchers Wear Jackets on Base?
MLB Pitcher: 15 Things You Should Know
What is the Average Velocity of a Division 1 Pitcher?
Top 17 Slowest MLB Pitchers in History