The highly experienced defender has fallen down the pecking order since the arrival of Maurizio Sarri and he will have to leave the Blues in order to play regularly.
The 33 year old has not started a single Premier League game for Chelsea this season.
Aston Villa should provide him with an exit route in January. Dean Smith could do with someone like him.
The Championship outfit will have to improve defensively if they want to secure promotion and Cahill has the quality to make big difference for them during the second half of the season.
Given his situation at Chelsea, he is unlikely to cost a lot either. He could prove to be a massive bargain in the end.
Smith could pull off a masterstroke if he manages to sign the former Premier League winner in January.
The move for James Collins collapsed after the defender injured himself and Cahill would be a superb alternative.