Mariano Rivera: Is He the Greatest Pitcher of All Time?

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Mariano Rivera, the only unanimous inductee to the Baseball Hall of Fame, is widely recognized as the greatest relief pitcher of all-time and solidly in the conversation for greatest pitcher overall. But how different from the rest was he really?

In this analysis, I will look at pitchers' cumulative impact on wins through the lens of Win Probability Added (WPA) and analyze the rate at which pitchers contribute wins to their teams through WPA/Innings Pitched. With this approach, I aim to offer insights into Rivera's standing within the overall pitching landscape.

Figure 1 below illustrates WPA/IP vs WPA for the 100 pitchers with the most WPA in MLB history.

Figure 1: WPA/IP vs WPA for the 100 pitchers with the most WPA in MLB history. The number of seasons the pitcher pitched is in parentheses after his name. + next to the pitcher’s name signifies that he is in the Hall of Fame. Active pitchers also have their ages listed after the number of seasons they’ve pitched.

The elite starters are circled in the bottom right quadrant of the graph, as they accumulated the largest WPA over their careers with their combined success and volume of innings pitched. Lefty Grove, Roger Clemens, Greg Maddux, Warren Spahn, Tom Seaver, Pedro Martinez, Randy Johnson, and Clayton Kershaw are on this list.

The elite closers are circled in the top left quadrant, as they accumulated WPA at the fastest rate, used almost exclusively in high leverage situations, but did not have the combined effectiveness and longevity to accumulate as much WPA as many starters. Jonathan Papelbon, Troy Percival, Joe Nathan, Craig Kimbrel, Billy Wagner, Kenley Jansen, and Trevor Hoffman highlight this list.

Rivera, however, is in a quadrant entirely of his own. At the intersection of elite starters and elite closers, Rivera sits with the fifth highest cumulative WPA and by far the highest rate of WPA accumulation, 13% higher than the runner up.