When Fingers reached the major leagues, the role of relief pitchers was limited, as starting pitchers rarely left games while holding a lead; but as team offense increased following the 1968 season, and especially with the American League's introduction of the designated hitter in 1973, managers became more willing to replace starters in the late innings with a lead in order to forestall any late rallies by opponents. Through the 1960s, both leagues' annual saves leaders tended toward totals of 20-25 saves; few pitchers remained in the role more than a two or three years, with significant exceptions such as Roy Face and knuckleballer Hoyt Wilhelm. But in the 1970s, in an era allowing for greater opportunities for closers than had previously been available, Fingers' excellence in relief allowed him to gradually increase his annual saves totals past 30. He eventually earned 341 career saves, greatly surpassing WIlhelm's record of 227.

Fingers is regarded as a pioneer of modern relief pitching, essentially defining the role of the closer for years to come. As had generally been true in baseball through the 1960s, Fingers was originally moved to the bullpen - and eventually to his role as a closer - due to struggles with starting. Before Fingers' time, a former starter's renewed success in the bullpen would have led back to a spot in the starting rotation; but since the successes of not only Fingers but also contemporaries such as Sparky Lyle and Goose Gossage, it has been widely accepted that an excellent pitcher might actually provide a greater benefit to his team as a closer than as a third or fourth starter. (Gossage, for example, was moved to the starting rotation after a first few seasons in relief---and he got clobbered, moving back to the bullpen to stay.) As a result, later teams have been more willing to move successful starters - notably Dennis Eckersley, Dave Righetti, and John Smoltz - to the permanent role of closer, with no plans to bring them back to the rotation (Although Smoltz bucked that trend by successfully returning to the rotation in 2005). As of 2006, Bruce Sutter---considered the working father of the split-finger fastball (a cousin to the forkball, a pitch Fingers himself used later in his career)---became the only pitcher in baseball history elected to the Hall of Fame who never started a game in his major league career.

Fingers won both the American League MVP and Cy Young Award in 1981 while with Milwaukee. In 1974 he was given the World Series MVP Award while with Oakland, earning two saves and one win. Fingers won the Rolaids Relief Man of the Year Award in 1977, 1978, and 1980 with the Padres and in 1981 with the Brewers. He saved 29 games for the 1982 Brewers, but he pitched most of the season in pain and was forced to miss the postseason that meant the Brewers' first trip to the World Series---where they were beaten in seven games by the Cardinals---and might have meant a showdown or two with Bruce Sutter, who proved vital to the Cardinals' winning effort.

In 1992 he was inducted into the Baseball Hall of Fame, joining Wilhelm to become only the second reliever inducted. In 1999, he ranked Number 96 on The Sporting News' list of the 100 Greatest Baseball Players, and was nominated as a finalist for the Major League Baseball All-Century Team. Fingers later pitched a season in the short-lived Senior Professional Baseball League.