Diego Costa is back in training. He trained with his teammates on Tuesday for the first-time since a reported bust-up with Antonio Conte. Chelsea have made it clear that they will not sell their star player in the January transfer window. The question is – how long can they keep him at the club

Tianjin Quanjian, the Chinese Super League club, tried to sign Costa this month, with the club’s owner, Shu Yuhul, having reportedly met the striker’s agent, Jorge Mendes. The Chinese club had also targeted Paris Saint-Germain’s Edison Cavani, Karim Benzema of Real Madrid and Monaco’s Radamel Falcao.

According to reports from the Guardian, Costa is unlikely to extend his stay at the club beyond the summer. The Chinese club are expected to rekindle their interest in Costa. Chelsea are “resigned to the reality” that they will not be able to tie the striker down to a new contract at the club.

Real Madrid striker, Alvaro Morata, remains Conte’s first choice option, should Costa leave the club. The other back-up options are: Everton striker Romelu Lukaku, and Arsenal forward Alexis Sánchez.

Chelsea are “tracking” the Sanchez’ contract stand-off with Arsenal, and will move for the Chile international in the summer. Sánchez, who earns £130k-per-week at Arsenal, will have just one year left on his current deal, and he is yet to commit his future to the London club.

Lukaku, the Belgian striker, is keen on a return to his former club. The striker has expressed time and again that he wants to play in the Champions League, and should an offer arrive, he would not hesitate to jump the boat. The 23-year-old has scored 18 goals in 25 appearances for club and country this season. His agent, Mino Raiola, has refused to rule out a summer exit.