Well, yes and no... Heskey has been injured regularly since he's been with us. In fact, it's rare that he and Carew have been fit together - when one is fit the other is injured, and so on. Gabby was injured before Houllier took charge; Petrov was injured in a game (and was probably due an injury, he's in his 30s and has been played/flogged to pieces over the last couple of years). Dunne hasn't really been right since the summer.
I think it's a coincidence.