Atletico Madrid have reportedly informed Chelsea that they only want to sign Alvaro Morata on loan, putting the transfer in jeopardy.
The Spanish club have been in talks with the striker in recent days, giving the 26-year-old hope of ending his disappointing spell at Stamford Bridge.
Morata has nine goals in 23 appearances this season and is no longer part of Maurizio Sarri's plans, having been left out of the squad entirely to face Newcastle United last weekend.
Sevilla pulled out of a move for the Spain international at the end of last week, claiming that it was "impossible" to reach an agreement with Chelsea, and the Daily Mail suggests that Atletico have also been unable to agree terms on a permanent contract.
Diego Simeone's men are now refusing to buy the player outright, it is claimed, and they are instead only interested in a six-month loan.
Chelsea signed Morata from Real Madrid in a £58m deal in the summer of 2017, but he has failed to match the form shown at Madrid and Juventus, when he was largely used as a back-up striker.