After an incredible 22-year career, the Big Unit has decided to hang it up.

Randy Johnson announced his retirement on Tuesday night and just like any sports fan or columnist does, we can’t just enjoy his career: We have to dissect it and compare it to others.

SI.com’s Tim Marchman broke down the battle between Johnson and Sandy Koufax while posing the question: Is the Big Unit the greatest left-hander of all-time?

During his five-year peak, Koufax ran up a 111-34 record with a 1.95 ERA, striking out 1,444 in 1,377 innings. From 1998-2002, Johnson’s record was 100-38, with a 2.63 ERA and 1,746 strikeouts in 1,274 1/3 innings. Koufax won five straight ERA titles, leading in strikeouts and wins three times and innings twice. Johnson won three ERA titles and four strikeout crowns while leading in innings twice and wins once.

Taking these numbers at face value, you’d say that as marvelous as Johnson was at his best, Koufax was that much better. But then Koufax pitched in a great pitcher’s park in a great pitcher’s era, while Johnson pitched in good hitter’s parks in a great hitter’s era. Going by ERA+, which adjusts for park and league effects and indexes them on a scale where 100 is average, Johnson actually has the better of it over their five-year primes, 175-167. Perhaps more impressively, he led his leagues in ERA+ four times during his best five year run. Koufax did that twice.

What makes Johnson so special isn’t that he had a five-year run to rate with Koufax’s prime, though; it’s what he did outside of it. Leave aside that run from 1998 through 2002 and Johnson’s career record is 203-128 with a 3.28 ERA –essentially Curt Schilling’s entire career, Hall-worthy in its own right. Add Koufax’s prime to that and you have something unfathomable, something that I’d say rates as the best career any left-hander has ever had.

This is a great debate, but I’m going to stay out of it because I never saw Koufax pitch and therefore, it would be unfair for me to proudly boast that the Big Unit was better. All I’ll say is that Johnson was one of the greatest pitchers I have ever seen in my era and I’m going to miss what he brought to the mound every fifth day.

The thing that often gets overlooked when people gush about Johnson is that he was a great student of the game. Even over the last couple years as injuries started to take their toll on his performance, nobody studied opposing hitters more than the Big Unit did before he took the hill.

Yes, he was a great intimidator with an electric fastball and outstanding strikeout ability. But the guy also loved the game of baseball and in an era of steroid abusers and cheaters, fans can appreciate what the Big Unit brought to the table.

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