Owner Roman Abramovich is said to be prepared to pay the £13.2m release clause in the Porto manager’s contract to bring him back to Stamford Bridge, where he previously worked when Jose Mourinho was at the helm.
“Villas-Boas has a contract and a release clause of €15m (£13.2m),” Porto president Pinto da Costa told Sport TV. “If someone deposits that in our account and he wants to go, we can do nothing because it is something that is contractually specified.
“If it does not happen then he will not be going anywhere and we will not do anything to make any negotiations easy.”
The 33-year-old led Porto to take the Portuguese league and cup titles as well as a Europa League victory.
Guus Hiddink had been the favourite to replace Carlo Ancelotti, although it is possible that he and Villas-Boas could work alongside each other as manager and sporting director.