In short, very.
He is unquestionably the greatest relief pitcher of all time, given his longevity, durability, and success from April through October. And, in my eyes, his 2008 season was the best season ever by a relief pitcher.
Rivera, who was 38 last year, posted a 1.40 ERA in 64 games. In 70.2 innings, he allowed 41 hits, 11 runs, while walking six and striking out 77. That's better than a 1:12 walk to strikeout ratio. It's absolutely mind-boggling.
Rivera posted a WHIP of 0.665. It was the sixth season of his career where his WHIP (walks and hits per innings pitched) was below 1.000. He also posted an ERA+ of 317, which was the best mark ever in the history of the game.
Want more stats? These are his career postseason marks:
W-L: 8-1, G: 76, ERA: 0.77, SV: 34, IP: 117.1, H: 72, ER: 10, BB: 16, K: 93.
Rivera has pitched in 26 career postseason series, and yet he has allowed just ten earned runs.
Oh, and by the way, he throws only one pitch (for the most part.)
Even though the Sandman will be 39 this year, I am sure he'll be back to his old tricks again in 2009. We will never see another one quite like Mariano, and as Yankee fans, we should enjoy his dominance and savvy on the mound while we can.
Read more of my commentary at bronxinsider.vox.com.