"From what I know from my chief executive, there has been an approach from a Premier League club," said Andre Villas-Boas. "It is a player who we have accepted a transfer request for, so we have to listen to offers."
The deal concerning Bolton defender Cahill is still going through the motions, with reports suggesting that the former Premier League champions may pull out of negotiations if the 26-year-old doesn't agree personal terms today.
"Still an ongoing negotiation, not that we don't want it resolved as soon as possible," he added. "I'm sure that all of the parties are protecting their interests."
The Blues will take on Martin O'Neill's Sunderland side at Stamford Bridge on Saturday.