A correction and clarification is in order.
I realize now I did not report as accurately as I wanted what I saw.
First, my vantage point during the race was from across the track and up a deck in a 50,000 seat stadium. I thought Centro was limping favoring one leg over the other when he dropped out. Others watching on TV agreed with me. The starter of the thread "Centro DNF Paris 1500" http://www.letsrun.com/forum/flat_read.php?thread=5274026 who was watching on TV said the same thing.
People in that thread point to him grabbing his hamstring. I don't see it rewatching the race video now.
I did say "what appeared to be his hamstring" but should have pointed out I was directly across the track and a deck up in a 50,000 seat stadium. I think I saw Centro jump the rail which looks like a limp and then saw himself put his hand high up on his hip. People in the thread say hamstring, but watching closer videos I don't see it.
(i've got it set to start where he drops out).
I've watched a few videos of the race now and don't see problems with the hamstring anymore.
This video was shot by a guy in the stands and shows some of Centro after dropping out. http://www.youtube.com/watch?v=URYAS8vt3q0#t=2m53s (it's set to start at 2:53 into the race).
I'm in the US and can not see the Universal Sports stream at this link: http://www.letsrun.com/news/2013/07/2013-paris-areva-diamond-league-video-highlights/ but I assume it's the first race video from above.
As for the mixed zone comment, Centro walked through very slowly through the mixed zone. Now that his camp says he's fine I can't say for certain he was limping. You can see Centro very briefly in the video here: http://www.youtube.com/watch?v=NRCLwS7UxU8#at=55 (it's set to start at the 55 second mark) and the 6 second mark here: http://www.flotrack.org/video/716937-Leo-Manzano-rocks-the-plain-black-top-to-run-the-standard
I should have written "walked slowly and gingerly through the mixed zone." I was talking to Leo Manzano at the same time so my focus wasn't 100% on Centro. In hindsight, I think I immediately thought of his walk: "yeah he's limping from his hamstring" as I was operating under the assumption he was injured from watching the race. Konrad Surkont, a collegiate runner for Harvard, was assisting me in LRC's coverage in Paris. This was his first time in a mixed zone. He agrees Centro walked very slowly, but said "exactly say how he was walking to be perfectly honest."
My description "visible limp" was inaccurate. It gives the impression he was hobbling through the mixed zone. He was walking very slowly and at the time I thought favoring one leg.
But that's an assumption I was making which I shouldn't have done.