Chelsea midfielder Eden Hazard will miss Thursday's Europa League tie against Belarusian side BATE Borisov with a back injury and faces a race to be fit for Sunday's Premier League game against Burnley, manager Maurizio Sarri said.
The Belgium international has been Chelsea's best performer with seven goals in nine Premier League appearances for the club so far this season.
"(Eden) is out," Sarri told a news conference on Wednesday. "He's got a back problem. We're trying to solve the problem for Sunday."
The Italian, whose team are third in the Premier League and top their Europa League group L with two wins in two games, also said he would rest midfielder Jorginho, who has started all nine of Chelsea's league games so far.
"We have to play after five days from the last match," Sarri said. "The problem will be on Sunday as we have to play after 65 hours. We have to change something. Jorginho needs to rest now."
Chelsea's last match was an acrimonious 2-2 draw with Manchester United that ended in a melee after Sarri's assistant coach Marco Ianni exuberantly celebrated a late equaliser in front of the opposition bench.
Ianni's celebrations sparked an altercation with Manchester United manager Jose Mourinho on the touchline and he was subsequently charged with improper conduct by the Football Association.
Sarri and Ianni both apologised to Mourinho after the incident and the Italian said he wanted to give his assistant a chance to redeem himself.
"As I said after the match, we were wrong," Sarri added. "I was there when Marco spoke to Mr Mourinho and he said sorry immediately. He realised he was wrong.
"I want to give him another opportunity. He was really sorry and he realised the mistake."
