Chelsea assistant Arno Michels has acknowledged that Mason Mount will undergo further examinations to see if he can participate in next week's Club World Cup.
Mount was forced off during extra time of Saturday's FA Cup tie against Plymouth Argyle, a game in which Chelsea recorded a 2-1 victory courtesy of Marcos Alonso's late goal.
Speaking after the match, Michels - who was standing in for Thomas Tuchel after the head coach tested positive for coronavirus - has hinted that it was injury, rather than cramp, which led to the playmaker being substituted.
Michels told reporters: "He felt an injury in extra time with this shot. He realised quick he felt pain and so we took him off.
"There will be further exams. Hopefully, it's not too bad but I can't promise what the situation is."
Mount had earlier provided the assist for Cesar Azpilicueta's equaliser in the first half.