However, Moyes has been impressed with both of them, particularly the Serbian international.
"Rio Ferdinand and Nemanja Vidic are two top centre-halves," Moyed told reporters. "Vida is probably the best centre half I have ever worked with. He is that good.
"Rio has really impressed me how fit he has been. He has not missed a day's training since we've been back.
"I don't know about Vida's contract. I have not looked into it yet. I am sure the chief executive and the club will be doing that. He's not old. He is a really top centre half."
United face West Bromwich Albion this afternoon.