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.

(“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.

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.

(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.

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.

(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