Dexter Fowler makes plate discipline mistakes in the worst moments

What separates good plate discipline from bad? Everyone knows that Joey Votto has a better eye than Delmon Young does, but is Votto better than, say, Jose Bautista? And if so, by how much? We can look at the issue a few different ways, all of which have some merit. Some disagreements will inevitably arise, however, as the case of Dexter Fowler illustrates pretty handily.

After a chaotic few days, Fowler officially rejoined the Cubs last week. Other people, such as my colleague Nick Stellini, have discussed the overall value he'll bring back to Chicago, but I want to zoom in on his plate discipline. For his career, Fowler has a 12.2 percent walk rate (that's good) and a 22.2 percent strikeout rate (that's bad)*. The simple version of his story ends there; the complicated version comprises the rest of this post.

*And no, he doesn't come with a free frogurt.

Let's begin with O-Swing rate. Many people will look at plate discipline binarily: If a hitter doesn't swing at pitches outside the strike zone, he has discipline, and vice versa. In that way, Fowler certainly fares well. According to FanGraphs' PITCHf/x data, he's offered at 21.9 percent of non-zone pitches over the course of his career, which ranks 40th out of 483 qualified hitters. When it comes to laying off balls in the dirt, not many batters can top him.

That alone doesn't determine plate discipline, though, because a hitter can just decide to stop swinging at everything. Look at Luis Castillo, the leader on that list. Sure, he has a 15.9 percent O-Swing rate — but he pairs that with a 44.7 percent Z-Swing rate, which also paces the majors. Players in this mold will rack up a lot of balls while also suffering an unhealthy amount of called strikes. Discerning the difference between hittable and unhittable pitches separates the disciplined from the lazy. And in this area, Fowler really comes out ahead:

In each of the past five seasons, Fowler has swung at an above-average rate of pitches in the strike zone. Overall, he's done so 64.2 percent of the time since his 2008 debut, placing 183rd in that 483-man sample. That's a pretty rare combination — among the 94 players with an O-Swing rate of less than 24 percent, only eight have a Z-Swing rate above 63 percent:

Suffice to say that McCutchen and Jones make for some sweet company. Combine that with the fact that pitchers have shied away from Fowler — his 48.3 percent zone rate finishes 149th in baseball — and you get a hitter who avoids both strikes as a whole and looking strikes. In 2014, FiveThirtyEight's Neil Paine used Z-Swing and O-Swing to conclude that Fowler had the best plate discipline of any batter since 2012; Fowler's lifetime results certainly bear that conclusion out.

Fowler's story gets even better when we look a little deeper. While knowing when to swing obviously helps a hitter, it'll also make his life easier if he makes contact. Chris Iannetta, for example, has a career O-Swing rate of 19.2 percent, a Z-Swing rate of 66.8 percent, and a contact rate of 74.0 percent. The swinging strikes he's received from that have elevated his strikeout rate and harmed his offense.

By contrast, Fowler has hit the ball on 78.5 percent of his swings. That ranks 314th out of the 483; along with his low swing rate, it gives him a satisfactory swinging-strike rate of 9.1 percent. Avoiding both looks and whiffs isn't a unique skill — Jones and his 81.5 percent contact rate can testify to that — but it is an uncommon one, making it all the more valuable for Fowler. The low O-Swing rate means he'll take walks, and the high Z-Swing and contact rates mean he'll keep his strikeouts in check. From top to bottom, his plate discipline impresses.

But Fowler has done only one of those things: As noted above, he's struck out quite a bit during his tenure in the majors, despite an average swinging-strike rate and a below-average looking-strike rate. What's caused him to underwhelm in this regard?

Let's return to that 483-batter sample. Using their swinging-strike rate and expected looking-strike rate, we get this equation and regression plot for an expected strikeout rate:

xK% = -0.1827 + 0.9240 * Look% + 2.2157 * Whiff%

Although this formula accounts for 83.4 percent of the variation in a hitter's strikeout rate, it has some flaws. Ten players have beaten their prediction by at least four percentage points:

Something has allowed opponents to fan Fowler despite his respectable peripherals. To figure out what, we'll have to dive into his situational splits.

A couple years ago, Chris Teeter graciously gave us major-league average looking and swinging strike rates by count. Using data from Brooks Baseball, we can get the same information for Fowler. How does he perform in this regard?

Not very well, it would seem. When Fowler's gotten to two strikes, he's swung and missed too often and taken too many called strikes. His more measured approach earlier in the count can't negate that later meltdown. There's also the fact that 28.5 percent of the pitches he's seen have come with two strikes in the count, which is a bit more than the 27.6 percent major-league mark. As his strategy gets worse, he's had more opportunities to mess up, on which he's "capitalized".

So Fowler has solid plate discipline overall, giving him a low walk rate; yet he has worse plate discipline in the most crucial times, which has inflated his strikeout rate. It all shows that we can evaluate plate discipline in a great deal of ways — from O-Swing to Z-Swing to contact to situational hitting. The surface rates make Fowler look pretty good; diving deeper reveals more.