Chelsea could be without top scorer Cole Palmer when they visit Premier League leaders Arsenal on Tuesday.
Palmer is the joint-top scorer in the league with 20 goals.
However, Blues boss Mauricio Pochettino said the 21-year-old is struggling to recover from illness in time for the game.
“We will see [Tuesday] morning. Today, I don’t believe he can be involved,” Pochettino said.
“Even if he is good [on Tuesday] maybe he is not in a condition to play. We hope he can recover from this situation and be involved with the team.”
Chelsea are ninth in the Premier League – three points off seventh place – and Palmer’s absence would be a blow for their hopes of qualifying for Europe.
However, it would be a boost to Arsenal’s aspirations of winning the Premier League for the first time in 20 years.
The Gunners’ hopes were dented by a 2-0 loss at home to Aston Villa on 14 April but they recovered with victory by the same scoreline at Wolverhampton Wanderers on Saturday.
Tuesday’s game will be Arsenal’s fourth in 10 days, but manager Mikel Arteta insists his side are not being affected by the quick turnaround between fixtures.
He said: “We are keeping on doing what we have been doing – focusing on the next game and the task ahead, preparing really well – as we have done in the time we have had available to us.
“The boys look ready to go again.”
Asked about the prospect of facing a Blues side without the goal threat of Palmer, he added: “I have no control over that, only on my players who are available.
“Whatever they [Chelsea] put out there, when you look at the squad quality they have is great.
“They are doing very well, they have good results recently and have been playing much better than their place in the table suggests.
“It will be a tough match, for sure.”
Defender Jurrien Timber is out for Arsenal as he continues his recovery from a serious knee injury sustained on his debut. He is set to play for the Gunners’ Under-21s this week.