The shelf-life of a baseball reliever

Ever since I read Moneyball, which turned me into a baseball stat super genius, as it did for everyone else, I have wondered about the value of a relief pitcher. For the most part, they come and go pretty quickly. Today’s top set up guy is tomorrow’s DFA.

Mason Miller, the A’s closer, has been fantastic. A lot of people think he’ll move at the trade deadline, as the A’s certainly don’t need him to finish last again. How much would you give up for him? If we’re just talking “We need a top closer to win the World Series this year”, fine. But how many years is he going to be a top closer?

My theory was three years is the max except for really top-end guys. The corollary to my theory is that this doesn’t apply to Mariano Rivera, who was the best reliever ever by a large margin. To test my theory, I finally got a subscription to FanGraphs, dumped all data for relievers from 2000-2024, ranked them by WAR each year, and then counted how many times a guy was in the top 25.

PlayerYears in the top 25 in WAR
Mariano Rivera12
Kenley Jansen9
Joe Nathan8
David Robertson8
Craig Kimbrel8
Aroldis Chapman8
Trevor Hoffman7
Rafael Betancourt7
Jonathan Papelbon7
Francisco Rodríguez7
Billy Wagner7
Joakim Soria6
Octavio Dotel5
Liam Hendriks5
J.J. Putz5
Greg Holland5
Francisco Cordero5
Edwin Díaz5
Ryan Pressly4
Roberto Osuna4
Raisel Iglesias4
Matt Thornton4
Mark Melancon4
Ken Giles4
Keith Foulke4
Josh Hader4
Jonathan Broxton4
Joaquín Benoit4
Huston Street4
Heath Bell4
Emmanuel Clase4
Devin Williams4
Dellin Betances4
Byung-Hyun Kim4
Brad Lidge4
Brad Hand4
Bobby Jenks4
B.J. Ryan4
Andrew Miller4

There you go. 39 players since 2000 have been top 25 relievers more than 3 years. I might redo the analysis a bit – WAR may not be the best way to rank a reliever.

I was definitely right about Mariano Rivera.

Rivera warming up
Mariano Rivera throwing in the bullpen, spring training, 2013. Photo by the author

Of the 318 players who ranked in the top 25 in WAR in the 2000’s, 192 did it once. 60 did it twice and 27 three times. The rest is the list above.

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