I don't think he's injury prone, he had one big serious injury with his hamstring at Everton and he's never been able to fully get into that Chelsea team but he's not been injured for a lot of it.
Can't really fault Villa for overusing him either, he played 90 mins for 5 games but we had 13 day break between Arsenal and Brighton. Anyone can do a hamstring and that's always been around a month out, it makes sense not to rush him with his history.
I think I remember Smith saying he has a chance for Burnley, which was now 2 week ago. Either that was just a total lie or he must have had some sort of set back that they are keeping to themselves.