Over the weekend Inter Milan made an approach for the brilliant young tactician, who led Porto to three trophies last season, including the domestic double and the Europa League.
Inter, though, baulked at the idea of paying his ?13.2million release clause, but that would not be an issue for Chelsea owner Roman Abramovich.
And reports from Portugal claim Chelsea have now turned their attention to the 33-year-old, who has already served as a coach at Stamford Bridge.
Villas-Boas is a protege of former Blues chief Jose Mourinho, and worked with him at Porto, Chelsea and Inter Milan before embarking on his managerial career in 2009.
After one year with Academica, he was appointed Porto chief in 2010 and he has blossomed.
Villas-Boas insisted after the Europa League final win that he was committed to Porto but that resolve now looks as if it could be tested.
And Da Costa admits he cannot stand in his way: "Villas-Boas has a contract and a clause of 15million euros.
"If someone deposits 15million euros into our account and he wants to go, we can not do anything because it is something that is contractually specified."
Chelsea have been locked in talks with Turkey coach Guus Hiddink about returning to the club.
The Blues have been talking with Hiddink about taking either the coach's job or the sporting director role, and should he take on the latter then there would also be, in theory, room for Villas-Boas to also come on board.
Source: Team Talk
Source: Team Talk