Chelsea manager Andre Villa-Boas has been blamed for the collapse of Alvaro Pereira's move to Stamford Bridge on transfer deadline day.
The Porto wing-back was set to make the move to west-London, with the two clubs only having to agree a fee.
However, Chelsea refused to meet Porto's £26.5 million asking price and the player's agent Flavio Perchman says the way Villas-Boas moved between the two clubs earlier this summer meant a deal was never able to agreed on.
“Unfortunately, the operation fell apart and there was no way it could be rescued," said Perchman.
“Porto have broken their word. Last year they promised to sell Alvaro Pereira if they received a proposal worth more than £18m.
“Chelsea made such an offer, but they cut off the possibility of Alvaro going, even though he is a player who has given everything for Porto. They refused all proposals.
"I think that Porto have used Alvaro Pereira to take revenge on Chelsea over what happened with Villas-Boas," Perchman added.
“Chelsea were interested for many days. Porto began by setting a certain value but Chelsea always tried to get closer than they intended to Porto. But Porto never relented.
“The frustration for Alvaro is that he had a promise. After the year he had for the club, helping Porto to win all they won, letting him move to Chelsea would have been his reward.
“Let’s see what happens in the future. But he will not stay any longer than he has to. We will see how he reacts.“