The agent of Alvaro Pereira feels Porto refused to sell to Chelsea as an act of revenge over their deal for Andre Villas-Boas.
Pereira had set his heart on a move to the Premier League after telling the Portuguese champions he wanted to follow Villas-Boas to Stamford Bridge.
Alejandro Savichara said: "When one side does not want to negotiate, there is not much you can do.
"I think that Porto have used Alvaro Pereira to take revenge on Chelsea over what happened with Villas-Boas."
