West Ham boss Zola: Difficult selling Collins to Villa
Zola said: "James is a player who has done really well for me and it was painful for me to let him go. Unfortunately we needed someone to go out so we could get a striker to come in. I explained that to him.
"He has gone to a good club though, they have treated him very well and I hope he does for them what he did for us.
"It is tough when you have a guy who was very much integrated with the other players and who is playing well but as long as you have nice and intelligent people like James, then it makes it easier to deal with things like this."