Villa are prepared to sell the Spaniard for £3 million.
McCoist said: "It's also common knowledge that Carlos is a big target, but we can't be held to ransom.
"His wages might be a bit of a stumbling block, but he is the type of player that we've got to target.
"We need players who want to play for the club. If he came back here he'd certainly give the whole place a lift. I would be absolutely thrilled if we could bring Carlos back."