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Still improving, Kershaw remains baseball's best pitcher

19.3 K/BB ratio would set MLB record by a wide margin
May 17, 2016

Clayton Kershaw shouldn't be able to get better. It shouldn't be possible that a pitcher already riding a five-year streak of top-three finishes in the National League Cy Young Award voting (winning three of them, as well as the 2014 NL MVP Award) actually still had room to improve. Yet

Clayton Kershaw shouldn't be able to get better. It shouldn't be possible that a pitcher already riding a five-year streak of top-three finishes in the National League Cy Young Award voting (winning three of them, as well as the 2014 NL MVP Award) actually still had room to improve. Yet here we are, watching him get off to a start in 2016 that would put him on track for the best season of a historic career.
That's how it looks from this view after Thursday's three-hit shutout in a 5-0 dismantling of the Mets, anyway. Kershaw's fifth consecutive start of 10 strikeouts with no more than one walk set a new Major League record, topping the four straight times Stephen Strasburg did it last year and 19 occurrences of three straight starts, including three Kershaw streaks. His strikeout-to-walk ratio has been so insane that whiffing 13 and walking one on Thursday actually represented a step back, dropping his K/BB from 21.3 to 19.3 -- which in itself would shatter Phil Hughes' modern record of 11.6 strikeouts per walk, set in 2014.
Kershaw's greatness is about more than just strikeouts and walks, obviously, but what he's doing with that 77/4 K/BB rate is so unprecedented that it's difficult to devote an undue amount of attention to it. Consider this: Every single year, Kershaw strikes out more hitters. Every single year, he combines that with fewer walks:

"OK," you're maybe saying. "He's great, but it's just eight starts. Lots of things can happen over eight starts." Fair enough, although it's more than obvious that Kershaw is hardly a small-sample fluke at this point. Let's instead look at Kershaw's past 32 starts, a number that may seem somewhat arbitrary but is generally accepted as "a full season of starts" for pitchers in the era of the five-man rotation. In 236 1/3 innings, Kershaw has struck out 305 against 30 walks, and has posted a 1.49 ERA and a 1.63 Fielding Independent Pitching (FIP) mark.
Now let's take that hidden "season" and compare it to the best pitching seasons of all time. Since the live-ball era began in 1920, there have been 4,019 seasons of at least 200 innings.
Best seasons, 1920-2016, Fielding Independent Pitching

  1. Pedro Martinez, 1999 -- 1.39
  2. Kershaw, 2015-16 (last 32 starts) -- 1.63
  3. Dwight Gooden, 1984 -- 1.69
  4. Bob Gibson, 1968 -- 1.85
  5. Sandy Koufax, 1963 -- 1.88
    Even when using a league-adjusted version that accounts for the changing run environments in baseball throughout the years, Kershaw's "season" still ranks second behind Martinez, just ahead of a pair of elite Randy Johnson years (1995 and 2001). As you can see, Kershaw's FIP just keeps on improving, as this look at his 32-game rolling FIP shows:

Why FIP and not ERA? Because ERA can be affected by quality of defense and bullpen along with batted ball luck, which the pitcher cannot fully control, and FIP is entirely based on strikeouts, walks and home runs, the "three true outcomes" that should be entirely within a pitcher's control. It's not a flawless measure, because it doesn't account for quality of contact against, but that's not exactly been a Kershaw issue either; he hasn't allowed opposing hitters to manage a batting average over .200 since 2012's .204, and after three straight years in the .192-.194 range, this year it's down to .186. In the two years of the Statcast™ era, his 85.6 mph exit velocity is tied for the lowest of any starting pitcher.
So what exactly is Kershaw doing differently in 2016 to actually up his production? He's not really throwing harder. Kershaw's spin rate isn't markedly different. He's throwing his slider slightly more at the expense of his curve, but not to an extent that stands out. It's hard to show huge differences when you're looking at a pitcher who was already great, though there are at least two things we can point to:
He's throwing more fastballs for strikes ...
"Walking guys is how you get in trouble," Kershaw told after beating the Mets. "I'd rather them string hits and make them swing bats to beat me, that's always my mentality."
Kershaw is right. Between 2010-15, between 55 percent and 58 percent of his fastballs were thrown in the strike zone. So far in 2016, that number is up to 65 percent. Considering that Kershaw threw more than 1,800 fastballs last year, a jump of 10 percentage points is nearly 200 more fastballs for strikes. Even Bartolo Colon, notorious for pumping fastballs into the zone, has never made it to 65 percent.
Among lefties who have thrown 200 fastballs, only Drew Smyly has more vertical movement than Kershaw's, which makes it very difficult to hit -- and is how he can get away with all those strikes. It's also how Kershaw has walked just four hitters all year (and one of them, to Hunter Pence, featured what was probably the most questionable ball call you'll see all season.) Kershaw doesn't have baseball's hardest fastball, or the highest-spin fastball. But he does have pinpoint control and the confidence in it to challenge hitters.
Gif: Clayton Kershaw fastball
… and he's using his curve more effectively.
Famously styled "Public Enemy No. 1" by Vin Scully back in 2008, Kershaw's curve has long been his most famous weapon. It's not necessarily moving more this year, showing 9.8 inches of vertical drop, since his career average is 9.3 inches of drop.
But Kershaw is using it differently. While we just hailed him for throwing more fastball strikes, he's throwing fewer with the curve -- his zone percentage has dropped from 47 percent to 38 percent to 28 percent. But the contact rate against it hasn't changed, staying steady in the 61 percent range, and that's not a bad thing.
Making hard contact on curveballs outside the zone is incredibly difficult, and of the 56 pitchers who have had at least 10 curves put into play, Kershaw's 79.6 mph exit velocity is the third lowest. Only twice of the 143 times he's thrown it has a hitter barrelled it up at more than 100 mph, and both of those times were groundouts to shortstop.
Gif: Kershaw Curve K Looking
Kershaw didn't need to get better, and in many ways it didn't seem posisble for him to get better -- yet, so far, he's been better. The results have been nearly unthinkable.
So with all due respect to Chris Sale, Max Scherzer, Noah Syndergaard and (especially) the phenomenal and historic in his own rightJake Arrieta, there's no need to be submitting resumes for the title of Best Pitcher in Baseball right now, because the position simply isn't open. The King isn't dead. Long live the King.

Mike Petriello is an analyst for and the host of the Statcast podcast.