The ways of Kerry Wood

Kerry Wood, as you know, used to be a starter. He had a full bag of pitches, including a fastball, cutter, curve and slider. A change-up, too.

Now he’s a seasoned closer, and he still can throw all his pitches. How he’s gone about using these pitches since being reinvented as a reliever is a little surprising.

During 2007, Wood showed each of his pitches, even two change-ups, in the occasional game that was covered by PITCHf/x. In 2008, when PITCHf/x went league-wide, he became a two-pitch pitcher a month into the season. Relying on his fastball and slider, Wood had a great season for the Cubs. A late-season revival of the cutter and even the curveball came along, and that may have been the first indication of what happened in 2009.

No, I’m not talking about the trade to Cleveland. I’m talking about the abandonment of the slider.

New look in 2009

The change in pitch mix is rather drastic, and I’ve carefully reviewed my pitch classifications to ensure accuracy. I think these two graphs tell the story—be sure to click for full-sized (i.e., legible) versions.

Kerry Wood pitch mix by season

Here’s another look, by game, without the fastballs.

Kerry Wood pitch mix by date

I can only speculate as to the “why,” but it could be anything from lessening arm strain to organizational philosophy/pitching coach preference.

Pitch results: 2008 vs. 2009

Here is where the speculation, for the most part, ends.

The one constant for Wood has been the predominance of the four-seam fastball. Whatever velocity he was lacking in 2007 has returned and stuck around.

May I Have Your Autograph, Please?
The payoff of being polite.

MPH Swing Whiff IWZ
2007 Fastball 94 0.511 0.133 0.615
2008 Fastball 96 0.540 0.197 0.582
2009 Fastball 96 0.456 0.213 0.561

(“IWZ” refers to the rate of pitches thrown in a “wide” strike zone. Two feet across, and as high and low as the hitter’s average PITCHf/x operator defined zone.)

Wood is throwing fewer strikes, although the trend could be a statistical mirage. You can’t argue that he’s throwing more strikes, though. Fewer swings and more whiffs in 2009 makes the lower IWZ rate look like it’s paying dividends. The downside, not shown in the above table, is an increase in both line drive and home rate. Seems a bit counter-intuitive, that he’d miss more bats yet give up more hard hit balls, doesn’t it?

The breaking ball

The clearest contrast between 2008 and 2009 is Wood’s swapping of the slider and curveball.

Swing Whiff IWZ Chase Watch GB% nkSLG
2008 Slider 0.353 0.411 0.502 0.265 0.559 67% 0.455
2009 Curve 0.224 0.294 0.408 0.156 0.677 88% 0.125

Clearly, the curve is not thrown often for strikes, but yields nothing but what look to be routine grounders. The whiff rate on the 2008 slider was excellent, but the curve is below average when it comes to missing bats.

Another difference in the two pitches is the counts in which they are thrown.

Count 2008 Slider 2009 Curveball
first 33% 9%
ahead 40% 29%
even 30% 11%
behind 8% 3%
full 25% 0%

(Percentage shown is of all pitches thrown in a given situation; the count groupings are mutually exclusive.)

It’s not that Wood, or the Indians, expect him to throw the curveball for strikes. It serves a different purpose, and isn’t nearly the favored pitch the slider was. Which brings us to the cutter, the key ingredient to the 2009 version of Kerry Wood.

Woody and the cutter

I recall Lou Piniella talking about Wood working on, and using, his cutter late last season. My memory isn’t as bad as usual in this case, as Wood did bring back the cutter in August of 2008. Wood’s cutter is a 90 mph pitch in 2009, so it isn’t to be confused with his 82 mph slider.

First, going back to 2007, here’s the situational usage of the cutter.

2007 2008 2009
first 6% 2% 20%
ahead 5% 3% 26%
even 2% 4% 25%
behind 6% 7% 18%
full 0% 5% 35%

Since the samples are so small from 2007 and 2008, I shouldn’t mention Wood’s cutter is cutting an extra inch and sinking a couple more in 2009. Oops.

The results are interesting.

2007/8 0.436 0.170 0.436 0.691 54% 23% 12% 12% 17%
2009 0.465 0.407 0.496 0.333 50% 28% 11% 11% 0%

(Last column is home runs per ball in air—FB+PU+LD.)

Combined, there are still only 55 cutters covered in the first row. There are 127 already in 2009 (though Friday’s games). The increased use as come with a nudge up in the IWZ rate but an explosion of whiffs. With a nearly identical batted ball type profile, the lack of home runs in 2009 is the only thing that seems to match the big drop in SLGCON (total bases on fair balls including home runs).

The new new Wood

New organization, new league, new approach. With all of the velocity, but fewer strikes, Wood’s fastball has been put to good use in 2009. With a new love for the cutter and a discarded slider, Wood has taken a three-pitch approach to attacking opponents. Now that he’s throwing cutters when he used to throw sliders, the breaking pitch has become a specialized weapon. The curveball gives hitters a different look than the slider, but it’s still a power pitch thrown almost as hard.

All things considered, I’d expect the new approach to cause less wear and tear on Wood’s fragile arm. While the ERA, WHIP and save rate posted for the Indians doesn’t look too good, there are a few points I’d like to leave you with:
{exp:list_maker}Wood’s walk rate is up, but last year was the anomoly
His K-rate is down one per nine innings, but is still in double digits
His home rate has increased four times over 2008, but, at 1.6, is due to fall {/exp:list_maker}
I can honestly say I’m happy the Cubs didn’t overpay for Kerry Wood’s services, and left that to the Indians. He may not be putting up the sexy numbers right now, but I wouldn’t forget about him in 2010.

References & Resources
PITCHf/x data from MLBAM
Pitch classifications by the author

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It is sometimes difficult to distinguish between cutters and sliders. Can you elaborate on the differences and why you consider Wood’s 2009 pitches cutters rather than modified sliders?

Harry Pavlidis
Harry Pavlidis

Not in Wood’s case. I’ll post some graphics and link ‘em here.

Harry Pavlidis
Harry Pavlidis

OK, four graphs, one covering all three seasons, then one each for 2007 thru 2009. The left panel will show the “spin movement”, the typical catcher’s eye view, in inches. The right panel will show speed on the y axis and spin axis on the x. I flip the direction of the x axis so the graphs “go in the same direction”. If anything, Woody’s slider and curve are trickier to separate. What I’m not showing are the game-by-game break downs, which actually make it clear what’s what more than these aggregated graphs will.