Villas-Boas, though, insisted he had set no deadline for a deal to be concluded and but was hopeful that would happen before the end of the week.
"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.
"I'm sure that all of the parties are protecting their interests."
Villas-Boas denied that Chelsea had made a reported £25 million bid for Lille star Eden Hazard but admitted he was a fan of the player.
The Chelsea manager confirmed Josh McEachran would go out on loan for the rest of the season - ostensibly to Swansea City - after Saturday's game with Sunderland.
He also said Gael Kakuta's loan move to Dijon had not been concluded yet but expected it to happen "soon".
The French club have announced the move on their website, but it is not yet finalised.
Meanwhile, Florent Malouda is a doubt for the Sunderland game after failing to train for the last two days.