As promised, here is the PFX analysis of Zambrano. One limitation I had was that this most recent start was in Tampa and this is the only time he's pitched there this year. Therefore some of the values might be not be the most accurate, but it is the best that we currently have so on we go.
To start with, looking at his release point, it appears that the whole game at Tampa Bay he was release the ball lower. This can both occur due to and cause an injury to the shoulder and elbow. Instead of the shoulder transferring the energy like a whip, some of the structures begins to fail as the energy is not transferred optimally for that person. In the next series looking at the release points across starts, it also appears that he wavers horizontally in his release point as well. As the release point comes closer to 0, his mechanics change. This can occur because he is dropping his shoulder, extending his elbow too late (again causing excess stress on the shoulder), releasing the ball later in the motion, or because of a purposeful mechanical change. I don't think it would have been due to a planned mechanics change or else we would have heard about it earlier.
Will Carroll of Baseball Prospectus have shown that control often goes first when an injury occurs. Looking at his pitch location chart, I don't really see any discernible difference between his home starts and his start against Tampa Bay.
It looks like he's consistent with his previous starts. Sure there are some that appears a little more inside, than others but overall they are spread apart evenly as expected. Normally the first sign of injury is loss of command but I think this is only in cases where the condition doesn't happen all at once, where it occurs over time. This didn't happen to Zambrano. He described it happening all at once, so the pitch location chart isn't very relevant to this discussion.
So looking at his velocity of his pitch types across the starts, it looks like there might be a slight dropoff in his fastball velocity (about 1 MPH). Again, this is ever so slight but because it is the average there are several better ones and several ones that are even slower that that. Looking at a table of his averages, you can see that almost all of his movement pitches were thrown at a less velocity in his last start than others.
Looking at his movement, across his starts. One interesting thing comes up.
In his last start, there appears to be more movement horizontally than in his other starts. It almost appears that everything is shifted to the left. Unfortunately, I cannot definitely say this is because of an injury or if this is a minute difference in the PFX setup.
Summary, evaluating PFX data across starts to evaluate a pitchers health is at it's infancy. Like others have noted, I'd love to be able to synchronize, the PFX data and video in order to get a true accurate read on a pitchers' mechanics. That doesn't mean that people shouldn't analyze what they have available to them though, this is the foundation of true understanding. As time goes on, we'll have better tools available to us.
Zambrano appears to have slightly changed his delivery in his last start. His velocity also suffered which can provide more information. Based on his symptoms and how he described it, I still believe there will be a labral tear and/or at least a partial rotator cuff tear. Unfortunately that means a lengthy stay on the DL and a possibility of ruining your chances of a fantasy crown unless you take action immediately.
UPDATE: This is why they do these kinds of tests. Despite describing symptoms that mimic a more severe problem, Zambrano was diagnosed with a "minor rotator cuff strain, but no structural damage" according to team officials. The plan though is still unclear which still leaves me wondering a little bit. I guess this is good news but in terms of returning to pitch, noone is sure right now. It all depends on how long his symptoms last. These things are notorious for being minor but resulting in a DL stay of longer than the minimum. Everything needs to be perfect or else he could do major damage during pitching. Hopefully more updates will follow relatively soon, so everyone can fully plan their lineups.