Yesterday Carlos Zambrano was scratched from his start with what the Cubs are calling a dead arm.  Apparently he has lost some velocity in his last few starts.  We can look at that with something I call  wear pattern.  Simply put, it is a plot of a certain pitch for a pitcher as the year goes on.  Here is Zambrano's four seamer wear pattern.

Let me explain how to read this plot.  First the horizontal axis is the number of the day throughout the year.  So his first start was at the end of March near day number 90 of 2008 and his last start on 8/24 was on day 236.  Next look at the black points.  These points represent Zambrano's fastball speed averaged for each day he pitched so they correspond to the left axis labeled "Average Fastball Speed".  You can also see error bars on these points which represent the spread on his velocity that day.  If he threw some pitches at 88 and some at 94 this is going to produce a large error bar.  If he was consistently in the 92-93 region it will produce a small error bar.  Lastly, the red and blue points represent the movement of the ball horizontally and vertically.  This corresponds to the movement axis on the right.  If a pitcher is altering his arm angle you can often see it in the movement.  For instance, if the horizontal movement is up and the vertical movement is down the pitcher likely dropped his arm angle.  This generally means a drop in velocity but not always.

Anyway, back to Zambrano.  Besides opening day when he threw so hard he wore his arm out Zambrano was in the low 90's for the first month and a half of the season.  His velocity slowly climbed to the mid 90's in late May and early June but after a trip to the DL, Zambrano has kind of been all over the map with his last couple starts back in the low 90's with a relatively high spread.  Notice that the movement of his fastball has barely changed at all so it is unlikely this has to do a change in arm angle.  What about Zambrano's bread and butter his sinker?

So the first things that jumps out at me here is the start before Zambrano went on the DL you can see very high spread in his sinker movement with particularly high horizontal movement.  This likely was caused by an inconstant release point that was probably a bit lower than usual.  While his velocity didn't suffer he clearly wasn't "right" but since coming back from the DL things appear much better.  Again there is a slight dip at the end in his last two starts but again, this is still in the range that you expect a Zambrano sinker to be in.  Ok Maybe there is something in his cutter.

Here in his last start before going on the DL his movement of his cutter was normal but the velocity of that pitch was very inconsistent.  That is particularly interesting because it is exactly backward what we saw with his sinker.  If there is a loss in velocity here I am not seeing it.  This looks like standard Carlos Zambrano to me.

To sum up, if there is a drop in velocity in Carlos Zambrano's fastballs it is a small drop at best.  I have heard reports that put his velcoity in the upper 80's in his last two starts and while a few of his pitches likely were there the majority of them have been in the low 90's were he has been all year.  As I pointed out in my previous article on Zambrano, his velocity is down a tick from last year so it is possible that a small fluctuation in his speed is causing more of a stir than it would have last year.