Clayton Kershaw’s Best Season

Occasionally, I use stupid as an adjective. Since I live in Kansas, I usually like to use it to describe the heat in summer. An example: “It’s so hot today, it’s unbearable. It’s stupid hot.” It’s probably not the best way to describe something, but what can you do? The reason that I bring this up is that I scrolled through some leader boards the other day on FanGraphs, and decided to look at the leaders for this season in xFIP-. I’ll explain why I use xFIP- in a bit, but the name that came up to the top was somewhat surprising to me considering his early season struggles. It’s none other than Clayton Kershaw, and it’s not really close. One might think that Clayton Kershaw’s best season was last year, but in fact, by xFIP-, Kershaw is having the best pitching season since 2002, and maybe one of the best pitching seasons ever. In other words, Clayton Kershaw is stupid good and we are in the middle of Clayton Kershaw’s Best Season.

Now, here’s a quick run-through on xFIP-. xFIP is short for Expected Fielding Independent Pitching. It’s a regressed version of Fielding Independent Pitching, which determines what a pitcher’s ERA should be with a normal BABIP (Batting Average on Balls In Play) and sequencing of runs. xFIP accounts for that as well, but also determines what a pitcher’s FIP would look like with an average amount of home runs allowed per fly ball in play. Home run rates allowed by pitchers are unstable over any given amount of time, though they generally settle back to league-average rates eventually. xFIP aims to account for this fluctuation to give a sense of a pitcher’s true talent level.

So what’s xFIP- then? Well, xFIP doesn’t account for park or league (AL or NL) adjustment, meaning that a pitcher’s xFIP could still be aided by advantages in league differences as well as differences from season to season. xFIP- adjusts for these, and gives a number to compare to other pitcher seasons. With xFIP-, 100 is considered average, below 100 is considered better than average, and above 100 is considered worse than average. So, a pitcher with a 90 xFIP- has a park adjusted xFIP that is 10 percent better than their league’s xFIP for the season.

Now that we’ve gone through that, here’s the leader board for xFIP- for 2015, according to FanGraphs:

Clayton Kershaw currently stands at a 51 xFIP-, which means he prevents runs at a rate 49 percent better than the league average. That’s stupid good. The next closest is Chris Sale, with a 62 xFIP-. Chris Sale is stupid good. Clayton Kershaw is eleven percent better than stupid good. And that’s just this year. When you look even further back into other seasons, Kershaw still looks stupid good. Here’s a table containing the same metrics, with the leaders since 2002 in xFIP-:

Now, we can only go back to 2002 since that’s the point at which PitchF/X started keeping track of fly ball rates. But this was a lesson for me, since Pedro Martinez is my favorite pitcher and the whole reason I’m even into professional baseball in the first place. Pedro’s peak began with the Red Sox in 1999, the season which many will call his best season and one of the best pitcher seasons ever. His dominance continued through 2003 (and to some extent, of course, the year to reverse the curse, 2004). Pedro’s 2002 is still one of the best pitcher seasons in recent memory. It stands fifth in ERA- (ERA adjusted for park, league, and season) and sixth in xFIP-. Pedro’s future teammate, Curt Schilling, actually had a better xFIP- in 2002 and has the best season xFIP- in the PitchF/X era. Or, had. As of right now, Kershaw’s 2015 is sitting just ahead of Schilling’s 2002.

While the chances of that number staying that low are probably slim, it’s possible. We could be watching a run of dominance like Pedro’s 1999-2003 unfold right before our very eyes. Look at what he’s given us with his last three starts:

26 innings, 38 strikeouts, NO WALKS, NO RUNS. He’s the first pitcher to post three straight starts with 10+ strikeouts, no walks and no runs since 1900. Remember, he started the season with an ERA of 4.32 after his April 21 start against the rival San Francisco Giants. People were wondering if he was hurt or if something was wrong. Since then, he’s been not only the best pitcher on the planet, but quite possibly one of the best pitchers we’ve ever seen.

His recent string of dominant starts is not only going to get him more Cy Young Awards, we can start talking about Hall of Fame. We can start talking about “greatest pitcher of his era.” He already looks like he might be this decade’s Pedro. Maybe he can be this generation’s Koufax. Stupid good, indeed.

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