Kinsler’s plate discipline

For the second year in a row, the Texas Rangers are in the World Series. A big part of their success could be attributed to second baseman Ian Kinsler, who hit for a .370 weighted on-base average and contributed in many different ways. Before we go any further, let’s take a moment to recap (and appreciate) all of the facets of Kinsler’s game in 2011:

{exp:list_maker}A stranglehold on the strike zone (1.25 walks per strikeout—best in the majors)
Plenty of power (a career high 32 home runs, tied for 12th most in the majors)
Speed (30 stolen bases, joining Matt Kemp, Jacoby Ellsbury and Ryan Braun in the 30/30 club)
Good defense (nine runs above average by FRAA, and 15 by UZR) {/exp:list_maker}

Today, I would like to pay attention to the first thing mentioned here. A huge component to Kinsler’s approach this year was his low strikeout rate. He struck out in only 9.8 percent of his plate appearances, which was 13th lowest in the majors. Though Kinsler’s been good throughout his career at getting the ball in play, 2011 was a career year in this department. And not only that: Kinsler also drew a career high 89 walks. Since 2008, his walk and strikeout rates have been trending in the right direction:

Year   K%  BB%
2008  11%  8%
2009  12%  9%
2010  12%  12%
2011  10%  12%

Please note that he walked plenty in 2007, at just under 11 percent per plate appearances; in this post, I’ll be looking at data from 2008 onwards since that was the first year for which we have full PITCHf/x data.

Walks and strikeouts may be easier to quantify than in-play events because they are a direct result of the batter/pitcher match-up, but there are still plenty of variables that could explain a change in walks or strikeouts. For the time being, I will take the binary in-zone/out-of-zone approach as seen on Fangraphs and now Baseball Prospectus, though this certainly has limitations (notably on borderline strike/ball pitches). I will be using the strike zone as defined by Mike Fast in this article.

Getting back to Kinsler, we can get a basic idea of what’s going on by using some generic in-zone/out-of-zone metrics.

Year    Zone%         Z-Swing%         O-Swing%      Correct%          Z-Contact%         O-Contact% 
2008   .513         .652             .257             .696           .930              .714
2009   .511         .662             .249             .706           .927              .726
2010   .501         .606             .218             .694           .944              .670
2011   .487         .575             .189             .696           .958              .750

It’s clear that Kinsler has become more selective since 2008, as evidenced by the decreased rate of swings outside the zone. The other factor at play here is that he is also seeing fewer pitches in his strike zone than he was a few years ago (49 percent in 2011 compared to 51 percentin 2008 and 2009). But at the same time, he’s also taking more pitches in the zone (called strikes), leading to a similar amount of “correct decisions.”

Maybe looking at Kinsler’s performance in different count situations could shed some more light on his improvements? I took the ball-strike permutations with an extremely favorable run expectancy for pitchers (0-2 and 1-2) and those with an extremely favorable run expectancy for hitters (2-0 and 3-1; 3-0 counts were excluded since swinging on 3-0 is so rare) and tried to draw some conclusions.


 Year       Zone%       Z-Swing%      O-Swing%
2008      .690        .653           .114
2009      .569        .725           .246
2010      .528        .632           .074
2011      .543        .596           .094


Year       Zone%       Z-Swing%      O-Swing%
2008      .358        .881           .376
2009      .385        .891           .369
2010      .282        .915           .376
2011      .299        .891           .304

To recap:
{exp:list_maker}When Kinsler’s in the driver’s seat, he’s seeing fewer pitches in the zone than he used to.
At the same time, he’s swinging at fewer pitches outside of his strike zone.
Behind in the count, Kinsler has been seeing fewer pitches in his strike zone than he used to.
When pitchers were in a position to put Kinsler away last year, Kinsler was less likely to swing at a pitch off the strike zone than he was in 2008, 2009, or 2010.
However, his rate of swings at pitches in the strike zone in pitcher’s counts has remained unchanged, meaning that he’s selectively aggressive. {/exp:list_maker}

So far, we’ve only looked at yes or no questions: Was the ball in the zone or not? Did Kinsler swing or not? What if we’re trying to examine the KIND of difference? If we want something a little bit less black-and-white, there are a few other ways to look at it. The graphs below show Kinsler’s swing probabilities by year in different regions of the horizontal strike zone, split up into two-inch wide bins and smoothed to accentuate the trends better.


The last thing I’m going to look at is swing area, as calculated by Josh Weinstock. The swing area, derived from a logistic regression equation, is used to describe how far the batter is willing to extend his zone. Patient hitters have low swing areas (under six square feet is the low range) and impatient hitters have high swing areas (Pablo Sandoval’s swing area is above 12 square feet). Applying this concept to Kinsler’s seasons gives us another way of showing Kinsler’s increased selectivity:

Year   Area
2008  7.69
2009  7.18
2010  6.89
2011  6.19

Josh will have a better and more thorough explanation of swing area, as well as some other plate discipline metrics, in an upcoming post.

It’s clear from the data we have that Kinsler has become a much more patient hitter at the plate over the past few years. He’s also benefited from having fewer pitches to hit in the strike zone, which has allowed him to take more walks. His contact rates on pitches in and out of the zone are excellent; his improving ability to take pitches when he needs to has helped turn him into one of the league’s elite hitters.

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