Kershaw Day: In the Unlikely Event Kershaw Never Throws Another Pitch…

Time will tell whether Clayton Kershaw can add to his collection of Cy Young Awards or not, but it’s a safe bet that the best pitcher in baseball has plenty of all-star games, playoff appearances, and magazine covers ahead of him. All pitchers are injury risks, of course, but Kershaw’s age, build, and track record of health suggests that he’s among the sport’s most dependable arms. He will probably have a long career.

But not necessarily. What if Kershaw, suddenly bored with dominating the National League and ambivalent about the $208 million left on his contract, decided to dedicate all of his time toward building shelters for impoverished children instead of throwing baseballs? Or, more plausibly, what if he did get seriously hurt? All pitchers are injury risks, of course, and any reference to Brandon Webb should be reminder enough of a hurler’s inherent vulnerability.

While we’d all be stunned if Kershaw were to call it quits tomorrow, the collective shock would last approximately 12 minutes before fans began debating where the southpaw’s firecracker career ranked among the all-time greats. In the more likely event that he doesn't, it's still an interesting discussion, even while Kershaw remains active. Has Clayton Kershaw's career surpassed, say, Fernando Valenzuela's? Andy Pettitte's? Tom Glavine's? Where does the comparing start, and where does it end? As always, one of the main hurdles when comparing careers is balancing peak and career value, and the challenge is all the greater when considering a player with such a short track record of success. Simply put, how do you rank the legacy of the durable but rarely dominant Pettitte against Kershaw’s three Cy Young awards? Against a Baseball-Reference page bleeding in bolded black ink but too brief to yet require a downward scroll?

To kickstart that conservation, let’s compare Kershaw’s career with some of the game’s best left-handed pitchers. We’re going to ignore the obvious: We know that Kershaw’s career isn’t over and that he’s as likely as any pitcher in baseball to win another Cy Young Award or post an 8-WARP season over the next few years. For now we’re pretending that the big lefty has heaved his last big-league pitch; we're evaluating where his career fits among the historical greats as it stands.

Even though he’s just 26 years old, Kershaw has already amassed more wins above replacement (B-Ref model) than all but 50 left-handed pitchers in baseball history. If we toss out the pre-World War II guys, he jumps up to 33rd. He’s also sixth among active left-handers. Of the five players he trails, only Cole Hamels began his career after 2002:

By June, Santana could be "retired" and Kershaw could easily be third on this list. As Impressive as that is, a closer look at Kershaw’s value places him in a class above his contemporaries. Using the WAR7 metric found in Jay Jaffe’s JAWS system—which aggregates WAR from the seven best seasons of a player’s career—we can see how Kershaw’s impact stacks up against the best seasons of other prolific lefties. For the sake of cleanliness, this table includes only post-20th century statistics:

(As always, a tip of the cap to Baseball Reference and their irreplaceable Play Index.)

Of the sixteen pitchers ahead of him, 10 are in the Hall of Fame already, and Santana will have plenty of supporters whenever his name reaches the ballot. In a world where Kershaw is about to hang up his spikes, his total body of work is actually pretty comparable to the Santana-Wood-Viola law firm. All three had a relatively short period of dominance, but at their peak, each could stake a legitimate claim to the title of ‘best pitcher in baseball’ for more than a fleeting moment. That Kershaw can compare is staggering: This metric measures the seven best non-consecutive seasons for each player, but in Kershaw's case it measures simply his seven seasons. That's all he's got to choose from. It includes his rookie half-season. It includes his pre-breakout 2009 season. If Kershaw could merely replicate his fifth-best season twice more, he'd be in a virtual tie with Koufax.

More impressively, few pitchers have been able to match Kershaw at his very best. While he hasn’t yet posted a historical season on par with Pedro Martinez’s run at the turn of the century, he is one of only eight lefties to accrue five WAR at least five times since World War II; the only pitchers to turn the trick more often are Johnson, Spahn, and Carlton. Furthermore, Kershaw is one of only seven southpaws to accrue six WAR or more four times in his career over that time.

Kershaw’s robust legacy is only enhanced when we move beyond WAR. While useful as a quick and dirty value check, the metric does a disservice to modern pitchers who generally don’t throw enough innings to compete on the same playing field as the workhorses of previous eras. On a rate basis, Kershaw’s numbers stack up well against anybody. His career ERA+ is 151, which is the highest mark for any left-handed starting pitcher with more than 1,000 career innings (he trails Martinez by a hair for the top spot overall). Kershaw also has the second highest SO/9 ratio, and is third in FIP among post-deadball southpaws. Lastly, even though walks plus hits per innings pitched is generally of little relevance outside of fantasy baseball circles, it’s still notable that Kershaw’s WHIP is the lowest figure in baseball history among left-handed starters.

The Texan also compares favorably in the black ink test, which is a quick and dirty way of saying that where there’s a metric, there’s Kershaw leading the league in it. He’s one of just 11 lefties — nine of whom are in the Hall of Fame — to lead the league in ERA+ multiple times and is one of just six southpaws to do it three times. While we’re at it, he’s also paced the Senior Circuit in WAR three times, strikeouts twice, and SO/9 once. He already has more black ink than the average Hall of Fame pitcher, per Baseball-Reference.

With only seven years of major-league experience, Kershaw would be ineligible for the Hall of Fame if he retired this spring. The 10-year minimum for enshrinement might be arbitrary and might lead the particularly passionate onto their soapboxes to vent about inertial reasoning and psychologically satisfying numbers, but it’s extremely unlikely that the Hall would relax its rules to admit a player with a seven-year career, regardless of the circumstances. But that doesn't diminish what Kershaw has accomplished. His run of dominance over the past four years is unmatched by all but a handful of pitchers, and he’s firmly placed his name in any discussion about the game’s best left-handed hurler. The easiest comparison from a career value perspective might be to Koufax, but even that seems to undersell his performance, as Kershaw has essentially produced the same value as the former Dodger great without the mediocrity that defined the first half of Koufax’s career.

For those compelled to obsessively rank anything and everything, determining Kershaw’s exact position among the best left-handers of all time depends more on your personal inclinations than anything else. Those who value consistency and durability might have inhibitions about placing Kershaw in their top 10; if you confine your scope to a pitcher’s very best three or four seasons, you can make a case for taking him ahead of anybody but Grove and Johnson. Out of respect for their longevity, I'd slide him behind Spahn and Carlton, too, but ahead of Hubbell, Koufax, and anybody else. The good news for baseball fans is that, elbow and shoulder willing, Kershaw isn’t going anywhere. For all of the discussion about Mike Trout’s historically sensational production thus far, crosstown Dodgers fans have essentially been treated to the pitching equivalent of it. Long may his career continue.