Unless you don't know what baseball is or what its stats mean, you're aware that Clayton Kershaw is having an incredible season. That shouldn't be news to baseball fans, either; should Kershaw maintain his league-leading ERA, it would be the fourth year in a row he's claimed that title, and unless something changes radically this should be the third time in four years that he brings home a Cy Young Award, the sole exception having resulted in a second-place finish. All of these accomplishments have come before the lefty has turned 27 years old. That's clearly great without the benefit of any additional background, but we can context this thing up and see where Kershaw's four-year stretch of dominion over Major League Baseball sits when put next to the history books. You know Dodgers fans are dying to know how Kershaw will ultimately stack up against one of their Hall of Famers, southpaw Sandy Koufax, but why stop there? There have been other amazing pitchers and four- or five-year stretches in this game's long history, and Kershaw's place among them says some eye-opening things about his own successes. Let's start in the obvious, logical place with Koufax, though: His greatest years came right near the start of the expansion era -- the one we care about when trying to gauge things historically, given how relatively little the game has changed since then -- with that epoch getting going in 1961, while Koufax's first Cy Young Award (and votes) came in 1963. From 1962 through 1966 -- when Koufax was forced to retire due to the abuse he had put his arm through in a 12-year career -- the lefty, who originally played for the Brooklyn iteration of the Dodgers, amassed nearly 1,400 innings with a 167 ERA+. He struck out over nine batters per nine at a time when pitchers just didn't do that -- the league average strikeout rate for starters in 1962, Koufax's top strikeout year, was all of 5.5 per nine -- and did it for years even before he became the Koufax of legend. Kershaw's performance holds up in comparison. Koufax led the NL in ERA for all five of those years, and Kershaw is currently on pace for four titles in four attempts. Kershaw's ERA+ is slightly better, at 172, and while his strikeout rate isn't nearly doubling the average like Koufax's, he's still punching out almost 11 per nine this year to lead the league and has the superior strikeout-to-walk ratio of the two. Most importantly -- and this is going to come up often -- Kershaw has done this from ages 23 through 26, and arguably hasn't even entered his peak years yet (assuming his health holds up). As Koufax reminds, a transcendent performance on the mound doesn't always mean health is part of the package for a pitcher, but the modern game also means Kershaw won't throw as many innings per year as Koufax. While Kershaw has a way to go before his career matches up with the elder Dodgers ace, his best work compares favorably, and if 2014 is any indication, it's not over yet, either. If your best can hold up when compared to Koufax, it can hold up against just about anyone. Bob Gibson has a plaque in Cooperstown, too, but his greatest stretch came from 1966 through 1970, when the Cardinals' ace posted a 153 ERA+ and 274 innings per year. Again, an innings comparison just won't work with pitchers from the distant past given Kershaw being limited by managers with a better sense of arm preservation, but that is not an insignificant gap in ERA+. If you're wondering when Steve Carlton is going to show up here, he won't, because he never had a stretch as long and successful as Kershaw's. Neither did Dwight Gooden, who, for all his excellence in 1985 and the surrounding years, shouldn't be in any discussion involving Kershaw beyond one comparing their similarly youthful debuts. Nolan Ryan is also left out in the cold here, because his career was more about the fact he spent 27 years doing his thing well more than any one single, Kershawian stretch of excellence.