England left-back Ben Chilwell is a doubt for the World Cup after suffering a hamstring injury in Chelsea's Champions League win against Dinamo Zagreb.
He was unable to continue and had to be helped off the pitch at full time as the Blues won 2-1.
"It doesn't look positive," Chelsea boss Graham Potter told BT Sport.
"It is the hamstring. We will have to scan it and see how it is."
England kick off their World Cup campaign in Qatar against Iran on 21 November.
Chilwell has been capped 17 times and was part of the England squad at Euro 2020, although he did not make an appearance during the tournament.