The England international is closing in on a move to Villa Park after his club Blackburn agreed to his sale.
Villa and Rovers are understood to have agreed terms on a deal, and the transfer should be concluded before the weekend.
Villa are hoping that Warnock could be signed in time to make his debut against Fulham on Sunday - a game you can see live on Sky Sports 1.
Warnock missed Blackburn's defeat at Sunderland last weekend, as Sam Alladryce admitted the player was on his way out of Ewood Park.
Talks with Villa soon progressed and now he is having his medical with a view to finalising his move.
"Stephen has had permission to talk to Aston Villa and we have got Pascal
Chimbonda talking here," said the Rovers boss.
"I think we have to get a replacement before we let Stephen go so if Pascal
gets done here I'm sure Stephen will get sorted out."