Cole Palmer was substituted during England U21s 9-1 victory against Serbia on Thursday with an injury, spelling more woes for Mauricio Pochettino.
The 21-year-old seemed to gesture to the touchline that he was in some discomfort and subsequently left the field on the 52nd minute.
Lee Carsley's European champions went on to secure a convincing win, but the injury sparked much concern among Blues fans online.
It comes after Palmer moved to Stamford Bridge in a £42.5million deadline day transfer this summer and has played nine games for the club in all competitions.