If there's a given in L.A. Dodgers lore, other than Vin Scully and Dodger Dogs, it's that Sandy Koufax is the greatest left-handed pitcher in team history, if not baseball history overall. You know the story: scuffled from 1955 to 1960, posting a 36-40 record with a league-average ERA, a lot of strikeouts (nearly 9 per nine innings) and a lot of walks (over 5 per nine innings). Starting in 1961, at age 25, he found his control, was an All-Star every year thereafter. From 1963 to 1966 he was absolutely dominating, winning 78% of his decisions with a 1.86 ERA, 9.3 strikeouts and only 2.0 walks per nine innings, collecting three Cy Young awards back when they gave out only one in all of baseball.
When he retired after that 1966 season, just 30 years old, due to arthritis, everyone assumed we'd never see another Dodger lefty like him.
Then, 22 years later, Clayton Kershaw was born.
Now, I'm not going to say that Kershaw is better than Koufax...yet. Kershaw is only 25 years old, and has been dominant for three of his six major league seasons, shorter than Koufax's four-year peak. But his last three years have been a Koufax-like run: through Sunday's game, a 70% winning percentage, 2.20 ERA, 9.1 strikeouts and 2.1 walks per nine innings. He won the Cy Young in 2011, was second last year, and appears to be the front-runner this year.
But wait, you're saying. Kershaw's 2.20 ERA is a lot higher than Koufax's 1.86. But there's more to that. One of the things I always look for when analyzing numbers is context. What were things like when numbers were accumulated? The fact is, baseball was different in the mid-1960s than it is today. The league ERA during Kershaw's peak was 3.85. The league ERA during Koufax's was 3.49. That's a difference of 0.36 runs. The difference between Koufax's ERA during his peak and Kershaw's during his is 0.34 runs. But wait, there's more: Dodger Stadium during Koufax's peak depressed scoring by 8%-9%. It's still a pitcher's park today, but the effect during Kershaw's time has been more like 5%-6%. So while Koufax's raw statistics are better, when you adjust them for the scoring environment and the stadium at the time he played, the advantage disappears.
One of my favorite websites is baseball-reference.com. It is a fantastic source of information that has helped make baseball encyclopedias obsolete. All my player links are to baseball-reference.com pages. Anyway, one of the calculations they do there is what they call ERA+. ERA+ measures how much better a pitcher's ERA than the league, adjusted for the pitcher's home ballpark. An ERA+ of 100 is league average. Anything above that is better than average. During Koufax's four-year peak, his ERA+ was 172. There have been only 125 times since 1901 that a pitcher has accumulated a single season ERA+ of 172; Koufax averaged that over four years. But Kershaw's three-year peak ERA+ is only negligibly lower, 168. Here are few more comparisons, adjusted for scoring but not stadium: strikeouts per nine innings 9.3 for Koufax an 9.1 for Kershaw, home runs per nine innings 0.7 for Koufax and 0.6 for Kershaw, baserunners per nine innings 1.04 for Koufax and 1.05 for Kershaw. Adjust those for the difference between the mid-1960s Dodger Stadium and the current iteration, and Kershaw pulls ahead.
There are two legitimate objections to the canonization of Kershaw. First, his peak has been shorter. That's fair, and why I'm not ready to call Kershaw a better pitcher. Let's see how 2014 plays out. Second, he isn't the workhouse Koufax was. Kershaw's never topped 233.1 innings pitched, while Koufax had 311 or more innings pitched in three of the four years during his peak.
I've got some problems with the latter argument. There's no question that Koufax pitched a lot more innings, just as starters in the 1960s pitched more innings than contemporary starters. But without getting into an argument about innings and pitch counts, let's remember that Koufax was done at age 30. Kershaw is headed toward a career high in innings pitched at age 25. When Koufax was 25, he was in is first All-Star season. At age 21, 22, 23, 24, and 25, Kershaw (69-39, 2.44 ERA, 155 ERA+) was clearly superior to Koufax (50-47, 3.92 ERA, 106 ERA+). If he can stay healthy (and stay signed with LA), Kershaw's on track to become the best, if not the most mythologized, Dodger lefty.