Atletico Madrid president Enrique Cerezo has said Diego Costa has not yet signed a deal to join Chelsea, but added that Blues goalkeeper Thibaut Courtois would not be returning on loan.
Costa, 25, helped Atletico to the Primera Division title and the Champions League final last season.
Towards the end of the campaign, reports emerged that the Spain international was heading to Stamford Bridge for an estimated 32 million pounds, and the player has said he is set to join Jose Mourinho's side later this summer.
Atletico chief Cerezo confirmed the Blues had been in touch about Costa, but said no deal had yet been struck for a player who has endured a disappointing World Cup campaign with La Roja.
"We don't know anything about Costa -- all we know is that Chelsea have made contact but we haven't received any money or anything else yet," he told a news conference.
"Until we receive the money from his buyout clause, he remains an Atletico player."
However, Cerezo implied that it would not be long before Costa was packing his bags for a move.
"We've always tried to convince our players to stay, but the difference between our finances and that of other clubs is very large," he said.
Chelsea have loaned goalkeeper Courtois to Atletico for each of the last three seasons, but Cerezo said the Belgium international's time in Spain had come to an end.
"Chelsea can count on Courtois, because he is their player," he said.
In addition to the likely departures of Courtois and Costa, Atletico have already bid farewell to David Villa, who has joined New York City FC, while Tiago Mendes has reached the end of his contract with the club.
Doubts also remain over the futures of defenders Filipe Luis and Miranda, although Guilherme Siqueira has joined from Granada.
"That's the way football is," Cerezo said. "We will try and get new players to come in who can score more goals or save more goals than the ones that are leaving."