I doubt its just dan smith, although it diodnt help. I think Diaby is basically made of glasss and was always going to be injury prone. Sad but thems the breaks.
Anyway he had the contract, and owes us nothing more than 100% comitment to get/stay available and to try to deliver when he is able/asked to.
As long as he hasnt slacked off thers not much more to be said other than 'bad luck.'