Chelsea's Reece James has twisted his ankle, according to manager Thomas Tuchel.
The defender's knock will be assessed to determine its full extent in the coming days, after being withdrawn on 29 minutes of the 1-0 home defeat to Manchester City on Saturday.
James had been involved in a collision with Jack Grealish and attempted to play on, but had to be replaced by Thiago Silva.
Tuchel said: "He twisted his ankle and it was very painful for him. I have no other news on him at this stage but let's see how he is in the next few days."
It puts James in doubt for Chelsea's second Champions League group-stage game away to Juventus on Wednesday.
The Blues are joint-top of Group H with Juve after beating Zenit St Petersburg in their opener at Stamford Bridge a fortnight ago; a game in which James played the full 90 minutes.
Tuchel has other options at right wing-back for the trip to Turin, if James is ultimately unavailable, including Cesar Azpilicueta and Callum Hudson-Odoi.
The German head coach admitted he could perhaps have made better selection decisions against City. stating: "'I think we lacked a little bit of freshness today.
"[N'Golo] Kante has been ill for some days and I decided to let him start. Jorginho has had some problems and Thiago could not start, so maybe today it is on me for not making the best choices in that sense.
"We decided on 3-5-2 but I don't think it's a matter of structure against City, it's about decisions and adapting to the opponent's spaces.
'We win together and we lose together. I will ask the questions of myself whether it was the right shape but I'm not sure the shape was decisive in the result.'