Tottenham defender Toby Alderweireld faces a period out of action after picking up an injury in Spurs' victory over Manchester City on Saturday.
The Belgian, 31, appeared to injure his groin and was replaced after 81 minutes as Jose Mourinho's side won 2-0 to move top of the Premier League.
Alderweireld has started six of his side's nine league games this season.
"I just feel sorry for Toby, because it was a fantastic performance. He has an important injury," Mourinho said.
Asked if it was potentially a long-term injury, the Spurs manager added: "I would say so."
Alderweireld tweeted after the match that he was "disappointed to pick up an injury", but "fingers crossed it's not too bad".
Tottenham host Ludogorets in the Europa League on Thursday (20:00 GMT) before facing London rivals Chelsea, who currently sit second in the Premier League, next Sunday (16:30).
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