Porto president Jorge Pinto da Costa insists there is no chance of the club agreeing to sell highly-rated full-back Alvaro Pereira in January.
The Uruguay international was a summer transfer target for Chelsea, with the Blues having a big-money offer knocked back.
It has been suggested that they will return for the 26-year-old in the New Year, with former Porto coach Andre Villas-Boas keen to bring a familiar face into his Stamford Bridge ranks.
Porto, though, have no intention of selling and Da Costa claims the reigning Portuguese champions will resist any approaches for their key men, with assurances having been given to coach Vitor Pereira that no players will be sold.
"I have offered a guarantee to the coach that no important players will leave the team in January, and that includes Alvaro Pereira," Da Costa told O Jogo.
"I think the chance to do a deal for this player has passed, and that is good news for us.
"Now is the time that rumours start spreading in the papers, but I am used to that."
Da Costa has also sought to play down speculation suggesting Colombian midfielder Fredy Guarin could be offloaded to Juventus for as little as €4million (£3.4m).
"That amount of money could only buy a youth team player from Porto," he said.