Manchester City have already had an opening bid of £20million rejected for Milner, who is preparing along with Warnock as part of Fabio Capello's provisional 30-man England squad ahead of the World Cup.
Warnock, speaking after England's 3-1 win over Mexico at Wembley, said: "I don't think the amount of attention James is getting is a surprise.
"I think everyone knows his ability and what he's about and what he's put in on the pitch at Villa this year.
"I think everyone knew his reputation before he even joined Villa, what he could be and what potential he had about him, and he's done very well.
"He can operate anywhere, he's very comfortable anywhere he plays and he's a quality player.
"I don't think the speculation (about his future) has affected him at all. You only have to see the way he's been in training and the way he played the other night (against Mexico). Nothing bothers him really, he just gets on with it."
Warnock added: "Of course, we want him at Villa next season but I think, if the price is right, it's very difficult for a club to turn it down.
"From his point of view, if there's a chance to play at a higher level, then it's something that I'm sure he'll be open to."