During Carlos Zambrano's last start I found myself chatting online with a Cubs fan in a large group of people and I made the comment that I was worried about his strikeout rate dropping the last few years.  He answered that it was because Zambrano was throwing his sinker more.  I wasn't so sure about this.  Zambrano throws three different fastballs and their movements are very similar so differentiating between them real time is definitely not something I could do. I also took a quite peak at his groundball percentage and it literally hadn't changed in the past two years.  Not that a ground ball percentage of nearly 47 percent is bad, it actually is quite good, but it hasn't changed in the last three years.  In addition, he hadn't really been lowering the number of pitches he was throwing per plate appearance (3.8 this year 4.0 the previous two years).  So why has his strikeout rate dropped from 8.9 per game in 2006 to 7.4 last year to 6.2 this year?  Also why has his walk rate dropped from 4.9 per game in 2006 to 4.3 last year to 3.3 this year?  If he really is throwing more sinkers early in the count then he likely should be getting more groundballs and definitely should be throwing fewer pitches per plate appearance.  Let's try to make some sense of what is going on here.

Starting with his 2007 movement chart we can see the jumble of fastballs.  His four seam fastball is right in the middle which he throws at 94.5 MPH.  It also doesn't have the rise of regular four seamers checking in at a tick under eight inches of vertical movement but a solid six inches of horizontal movement.  This is certainly due to his lowered release point which is generally a tad lower than ¾.  He is throwing this pitch 17 percent of the time more to lefties than righties (21 percent to 13 percent).

His sinker is a power sinker being thrown at 92 MPH and "rising" just under five inches.  Notice this pitch has more vertical movement than the classic sinkerballers you think of like Brandon Webb and Derek Lowe.  The reason for the is likely the extra velocity Zambrano is getting with his sinker.  Both Webb and Lowe generally throw in the upper 80's so Zambrano is trading off increased speed for increased movement.  Also because of lower arm slot this pitch really bores in to right handed batters as he generates just over eight inches of vertical movement. He is throwing the sinker 26 percent of the time slightly more often to righties than lefties (29 percent to 24 percent).

Zambrano also throws a cutter which gets almost no press.  This pitch only move two inches horizontally but almost seven inches vertically.  He also throws this pitch quite hard checking in at 91 MPH on average.  Despite basically nobody talking about it Zambrano threw this pitch the most of nay of his fastballs at 33 percent of the time and equally often to lefties and righties.  That is very unusual as pitchers who do throw a cutter tend to throw it more to an opposite handed batter as the ball rides in more than a regular four seamer would.

Zambrano also throws a slider and a splitter with most of the sliders against righties and most of the splits to lefties like you would expect.  He threw the splitter 14 percent of the time in 2007 and the slider 10 percent of the time.  Despite a quite large difference in speed and movement between his splitter and sinker Zambrano actually grips the two pitches very similarly.

Ok, on to 2008 Zambrano and here is his movement chart.

The first thing that jumps out at me is how his sinker has slightly diverged from his four seamer.  His sinker now has more horizontal movement up to nearly 9½ inches and it also is sinking about a half inch more.  He still is throwing this pitch at 92 MPH so that hasn't changed but with the added movement this clearly is a better pitch than it was last year.  As a result he is throwing it more, nearly 38 percent of the time, which is a large increase.  So if that Cubs fan is reading, you are reading you were right, more sinkers and better sinkers.

As a result, he is throwing his four seamer and his cutter less (11 percent and 24 percent respectively).  He also isn't getting the same velocity he was with those pitches with his four seamer down one MPH and his cutter down half a MPH.  That is kind of strange that he would lose a little velocity with those fastballs but keep the velocity on the sinker but that is what has happened.  Also, his splitter and slider have changed places with him throwing his splitter 11 percent now and his slider 15 percent of the time. 

The other thing that kind of jumps out at you is how spread out his pitches are now.  In 2007 everything was kind of nice and tidy and bundled together but in 2008 not only has his sinker spread away from his four seamer but his slider has become a smear instead of a cluster.  What is going on here is as Zambrano adds or subtracts spin the slider breaks more, or less, horizontally.  Normally when I see a pitcher who throws a pitch that is smeared out like that I question whether the pitcher is consciously doing that or if that spread is just due to lack of repeatability.  Here though I think it is very clear that Zambrano is in control of this as he showed in 2007 that he can repeat his delivery and produce a nice compact cluster of sliders.  Assuming this is the case this likely is a real weapon for Zambrano who can then throw the slider with little movement early in the count and throw the slider again late in the count when looking for a swing and a miss.  If you look hard you can see similar spread in hit cutter and sinker as well though the spread is less pronounced there.

So that was very interesting but how does this help us answer our questions we started with about the lowered strikeout and walk rate coupled with a tiny change in pitches per plate appearance and no change in his groundball rate.  Well it is clear that Zambrano is using his sinker more but even still that sinker isn't a beat the ball into the ground sinker so while he is still getting solid ground ball numbers that is the reason the ground ball percentage hasn't gone up even though the sinker percentage has.

What about the decreased walk rate and strikeout rate with nearly the same pitches per plate appearance?  Well, in 2007 Zambrano was using his fastball and his cutter a lot as his strikeout pitch.  In fact, 54 percent of the time he would throw either his fastball or cutter on 0-2 or 1-2.  This year that percentage is down to 40 percent.  Now he is throwing his splitter or his slider much more and if a batter lays off that pitch he Zambrano has to come back and throw more pitches.  I wonder if the decreased velocity on his fastball and cutter are the issue here.  High heat can be a very effective strikeout pitch but it tends to be even more effective if you can throw it 95 MPH.  Zambrano is throwing strike one more often this year than last so he is getting in pitchers counts more often so he is walking less but then isn't closing the deal so the strikeouts have suffered and the pitch counts really haven't been impacted either.