Christian Pulisic will miss Chelsea's next three matches because of an ankle injury, Thomas Tuchel says.
The 22-year-old winger suffered the injury during United States' 4-1 win against Honduras in World Cup qualifying.
Pulisic has already missed Chelsea's last two Premier League matches after contracting Covid-19 but is set to be out even longer, while N'Golo Kante is also unavailable.
What has been said?
"Unfortunately we have two players out, N'Golo Kante and Christian Pulisic, they both came back injured," Tuchel said in a press conference ahead of Chelsea's Premier League match against Aston Villa.
"N'Golo got injured against Liverpool and still suffers a little bit. We'll try with N'Golo for Tuesday, so this looks pretty good.
"For Christian unfortunately he came yesterday on crutches, and we have an ankle injury with about 10 days."
Which games will Pulisic miss?
As well as the Aston Villa encounter, Pulisic will miss his side's opening game of the Champions League group stage against Zenit.
He will also be out for the away match against Tottenham but could return for the Carabao Cup clash with Villa on September 22.
Who else is missing?
Chelsea may also be without Thiago Silva for Saturday's match after FIFA ruled eight Premier League players ineligible for this weekend's game.
The order came after the Brazilian football association urged the organisation to punish English clubs after they refused to release players for the World Cup qualifying games.
But Tuchel says there may still be a chance for the centre-back to play.
"Right now Thiago is not officially out. The chairman is still in negotiations and I'm waiting for the final decision," he said.
"For me it's enough if I get the final decision tomorrow. We will take the latest decision tomorrow morning and we still hope he can play."
He added: "I don't understand it and it makes no sense from whatever side you look. Did it make sense for Brazil? No. Did it make sense for us? No, because he may not be able to play two matches.
"If we had sent him, he would've been out for 10 days in a hotel room, not able to train. I understand because these are the travel restrictions, there's nothing to go around it.
"I don't know how any fan in this game can see a positive effect. There is none."