"Still an ongoing negotiation, not that we don't want it resolved as soon as possible," said Villas-Boas, who refused to criticise Cahill or his representatives over the player's wage demands.
"From what I know from my chief executive, there has been an approach from a Premier League club," said Villas-Boas.
"It is a player who we have accepted a transfer request for, so we have to listen to offers."
The Chelsea manager confirmed that the club were not prepared to listen to offers in the transfer window for Ivory Coast pair Didier Drogba and Salomon Kalou, currently on international duty at the African Cup of Nations.
Their contracts both run out at the end of the season.
Villas-Boas also confirmed that midfielder Josh McEachran would go out on loan for the rest of the season - ostensibly to Swansea City - after Saturday's game with Sunderland.