Chelsea manager Antonio Conte has admitted that the future of striker Diego Costa is uncertain.
The Spaniard is currently ruled out with a back injury that is expected to keep him out for at least three weeks.
Former club Atletico Madrid are interested in bringing the 27-year-old back to the Spanish Liga but Chelsea want to sign a world class striker before concluding the deal.
"I can say that today [Diego] Costa is a Chelsea player," Conte told reporters.
"He didn't play in these games because of injury and if he solves the injury and I see in training he's in good shape, it can be possible to see him in the next game against Milan. But I can tell only this.
"Today Costa is Chelsea's player. Tomorrow if you ask me if Costa will remain with us, I don't know.
"My target is to become a team.
"My experience as a player and a manager teaches me if you want to fight for the title you must be a team inside and outside of the pitch.
"It's important to understand this and transfer this thought on to the players. We must become as a family. This is the key to switch from last season. If we don't understand this it is no good."