Clayton Kershaw: Like a Boss (of the Strike Zone)

I’m sure I’m accidentally quoting dozens of able writers and analysts when I state that at the heart of a baseball game lies the pitcher-batter confrontation — and that, at the heart of that confrontation, is a power struggle over rights to the strike zone.

If, in some kind of alternate reality, a batter (for whatever reason) weren’t permitted to swing, it’s very possible that Josh Tomlin or Doug Fister or some other control artist would dominate the game. If, in a different reality from that, there were no such thing as a base on balls — that a pitcher just needed, say, to get three strikes — then Aroldis Chapman and his 13.9% swinging-strike percentage would be incredibly valuable (until such a time as his arm fell off, that is).

As it turns out, batters are allowed to swing and there are such things as four-ball walks — and it’s for these twin reasons that pitchers must employ all manner of spins and changes of speed and menacing scowls to defeat their opponents within the strike zone (or, if possible, tempt them out of it).

Currently — and somewhat unexpectedly, I’d suggest — the pitcher most frequently winning this battle for strike-zone supremacy is Dodger lefty Clayton Kershaw.

Which, more on him in a second. First, a note on how we might measure strike-zone supremacy.

The criteria for the totally fictional title of Boss of the Strike Zone isn’t particularly complex — in fact, criterion, singular, is more accurate: one needs only to look at how often a pitcher is walking batters versus how often he’s striking them out. Traditionally, this has been measured by strikeout-to-walk ratio (K/BB); however, in a series of posts (blam, blam, blam) at his very astute blog, the very astute Tom Tango (along with the help of his very astute readers) has demonstrated that, really, taking the difference between strikeout rate (strikeouts divided by batters face, or K%) and walk rate (walks divided by batters faced, or BB%) — what we’ll call strikeout differential (or K-BB) — is more representative of a pitcher’s ownership of the strike zone.

What makes all of this particularly relevant is that, just two weeks ago, Dark Overlord of FanGraphs David Appelman added both K% and BB% to the site. This makes it possible to find a player’s K-BB really easily. And if one were particularly motivated, he could find the K-BB for all 108 qualified starters in the major leagues.

One, being so motivated, would discover that the top-10 pitchers by K-BB are as follows:

The presence of Roy Halladay on this list is decidedly not surprising. Same goes for Cole Hamels, Cliff Lee, and Justin Verlander: all are known for pitching masterfully and all have appeared here in previous seasons. But the presence of Kershaw at the very top of the list, I think, is surprising.

There has, of course, never been any doubting Kershaw’s raw stuff. He’s a lefty who sits at 93-95 mph with his fastball, owns a nasty slidepiece, and has averaged over a strikeout per inning through his first three major-league seasons. The problem, of course, has been controlling said stuff: over those same first three major-league seasons, Kershaw allowed 4.2 walks for every nine innings (11.1% BB). This season, those numbers have dropped to 2.36 and 6.6%, respectively.

At the same time, Kershaw’s K% has been rising slowly, from 21.3% in his rookie season of 2008; to 26.4% and 25.0% in 2009 and ’10, respectively; and now to his current (league-leading) rate of 28.6%.

What’s behind Kershaw’s improvement? The exact reasons for that are outside of the present author’s skill set. The hard slider that Daves Cameron and Allen discussed back in April appears to be an actual thing: not only does Pitch F/x say that the slider has been 2 mph faster on average than the one he’s thrown the last couple years, but it’s also been worth more per 100 thrown (3.93 runs) than ever before (last year’s 2.77 runs per 100 was his high).

Mostly, though, we might say that, if some pieces at FanGraphs are strictly analytical, others are designed to alert the reader to changes in this or that baseball-related narrative. Previously, the popular narrative regarding Kershaw has been something like “great stuff, hard time controlling it.” However, that narrative is changing. Clayton Kershaw is officially the Boss of the Strike Zone at the moment. Baseball fans should adjust their assumptions accordingly.