As a Met fan who has become all too familiar with the talent of Mariano Rivera, be it through subjective means of simply seeing him throw that devilish cut fastball or becoming familiar with the sabermetric-centric numbers of his, he looks all the more impressive and I have even been inclined to give him the title of "Best Closer of All-Time".
Alas, this has all changed after a debate I had with my cousin, a sabermetrically-inclined Yankee fan. We were discussing the idea behind Andy Pettitte's HoF candidacy (we both said no) and Mike Mussina's (he said yes but not sure-fire, I said no but it wouldn't kill me if he got into the HoF). It was then that I said the following:
The only pitchers from that era who are locks in my opinion just by looking at the stats and not the win-loss record are Clemens (if he gets in), Pedro, Maddux, and Randy Johnson. I still can't believe how fucking good Pedro was from 1997-2003, his FIP in 1999 was 1.39.
He replied: throw mariano into that list too and we have a deal
I then countered with Trevor Hoffman, and he sent he the following list:
I thought I was shot to shit until I thought about something: How much does ERA+ really matter if you're a closer? I believe it makes all the difference for starters and pitchers who reach above a season threshold of 100 IP due to the DH, but how many pitchers do closers face regardless of the league? NL managers often employ the double switch or pinch hit to prevent their pitcher from facing the closer; the only way you will face the pitcher in a lineup in the 9th inning in the NL is if you implode completely.
If anything, all the other candidates look quite rosy compared to Mariano Rivera outside of Percival, so here's more stats for digesting:
Rivera: 2.23/2.73 in 1150 IP
Wagner: 2.31/2.73 in 903 IP
Nathan (everything from now on is from 2003- to reduce the effect of his starting #s): 2.04/2.62 in 497.2 IP
Percival: 3.17/3.87 in 708.2 IP
Hoffman: 2.87/3.08 in 1089.1 IP
I then realized why I missed people like Nathan, Percival, and Wagner: they miss the 1000 IP threshold that Baseball-Reference employs to keep career records, by this standard Mo Rivera is #1 all-time and Hoffman is #14. Include the other 3 and Wagner's #2, Nathan's #3, Percival's tied for 7th, and Hoffman's bumped down to 16th.
Here's their career WHIPs:
Since moving to the bullpen in 2003, Nathan has been nothing short of dominant and his 2006 season may be the most impressive for a closer in baseball history outside of Dennis Eckersley's 1990 statgasm of a season (yes, he had an ERA+ of 610 that year).
To be honest, you can make a pretty compelling case that if Nathan keeps up his dominance (a big if) and Wagner hits 1000 IP, Mariano Rivera is the third best closer of his era and he has been nothing short of brilliant.
So in closing, I offer you comparisons of Nathan, Wagner, and Rivera from Fangraphs regarding K/9, K/BB, HR/9, Opponents' Average, and WHIP in that order (I apologize for lack readability, Rivera = green, Wagner = orange, Nathan = purple)
I welcome all comments, gripes, corrections, and any other statistical analysis you may find relevant to the topic. I know this is a bare-bones post, but it really got me thinking.