There's a lot of talk about exactly how valuable a relief pitcher can be and whether any reliever can really be considered among the best pitchers of all time.
Well, I'd like to throw in one WOW number. I know... I know... I don't have to convince people that Mariano is a great pitcher. But humor me for a minute...
There is a sabermetric stat called Adjusted ERA+. In essence, this takes a pitchers ERA and it corrects for quality of the league, ballpark, era, etc., etc. Obviously, it's a much better stat than just plain ERA. There are more complete ways to determine how good a pitcher has been and to get a complete picture of how good a pitcher is, you need to look at things like WHIP, BB/9, K/9, OPS+ against, etc. However, I'm sure most would agree that so far as it goes, adjusted ERA+ is as good a stat as any to encapsulate a pitcher's performance in a single number.
ERA+ is measured as a percentage of the league average. An adjusted ERA+ of 100 means that the pitcher was exactly as good as the league average pitcher. 110 is 10% better than average, etc.
Okay. As you can imagine, relievers are over represented in the career adjusted ERA+ because relievers tend to have better ERAs than starters. They pitcher fewer innings and are thus less susceptible to getting tired and giving up a big inning. Fine.
However, they're not grossly overrepresented. Of the top 20 all time, 4 are modern era relievers. But most are starters and the distribution among various eras is noticeable.
Numbers 3-10 in this stat are:
There are only 18 pitchers in major league history with an adjusted ERA+ of 140 or better. Of these, 16 are in the 140s.
Pedro Martinez rings in with an extremely impressive 154, six points better than third place Lefty Grove's 148.
Pedro's adjusted ERA+ is the second best of all time.
What is his adjusted ERA+?