Major League Baseball (MLB) annually honors its best relief pitchers in the American League (AL) and National League (NL) with the Mariano Rivera AL Reliever of the Year Award and Trevor Hoffman NL Reliever of the Year Award, respectively. The awards are named after Mariano Rivera and Trevor Hoffman, who played their entire careers in the respective leagues. The awards were first issued in 2014, and replaced the Major League Baseball Delivery Man of the Year Award, which had been presented since 2005. Also that season, the Major League Baseball Delivery Man of the Month Award was discontinued. Though all relief pitchers are eligible, all recipients of the award have been closers.
The Reliever of the Year Awards are determined based on a vote of a nine-member panel made up of Rivera, Hoffman, Dennis Eckersley, Rollie Fingers, Goose Gossage, Bruce Sutter, Lee Smith, John Franco, and Billy Wagner. This represents the four living relief pitchers who are in the Hall of Fame along with the top five relievers in career saves. Each voter selects three pitchers for each league based solely on their performance in the regular season; a 5-3-1 weighted point system is used to determine the winner.
The Delivery Man Awards were initially part of a sponsorship agreement between MLB and package delivery company DHL Express from 2005 to 2010. From its inception in 2005 through 2008, the annual award was given to a single reliever that was selected online by fans from a group of 10 finalists chosen by an MLB panel. The panel took sole responsibility to select the annual winner starting in 2009. The winner of the monthly award was decided on by a four-man panel, which originally consisted of Dennis Eckersley, Jerome Holtzman, Rick Sutcliffe and Bob Watson. The panel has included Darryl Hamilton and Mike Bauman, a national columnist for MLB.com.