Jose Mourinho is concerned Toby Alderweireld will be out long-term with an apparent groin injury sustained in Tottenham's win over Manchester City.
The Belgium centre-back was forced off towards the end of Spurs' 2-0 win which sent them top of the Premier League, and replaced by summer signing Joe Rodon; his home debut.
Alderweireld was holding his groin as he hobbled off and, at full-time, when asked if the knock was a potential long-term injury, Mourinho told Sky Sports: "I would say so.
"I just feel sorry for Toby. He did a fantastic performance, he has an important injury. It's the injury of fatigue. It's the injury that happens
"But it was an opportunity for (Joe) Rodon to come into a game of this dimension and difficulty. So, let's go. Thursday we have another one."
Alderweireld had turned in a superb defensive performance, as goals from Heung-Min Son and Giovani Lo Celso gave Spurs their second successive home win over Pep Guardiola's side.
Alderweireld played two full games for Belgium during the international break, including the win over England.
Mourinho did not want to blame Belgium for the injury, but warned he is short of players for Thursday's Europa League clash at home to Ludogorets.
"It's bad. It's a muscular injury in his adductor. It's a difficult injury, for sure," he said. "In the Premier League we have three centre-backs. In the Europa League we don't have Joe Rodon, so only have two.
"But that's the way it is. There is nobody to blame. He played in the Nations League matches that his team had to win to qualify for the final four. He is playing so well so we decided not to rest him of course. There is nobody to blame, just to recover as soon as possible."
Alderweireld himself tweeted soon after the final whistle at the Tottenham Hotspur Stadium, stating: "Fantastic team performance/clean sheet/win today! Disappointed to pick up an injury, fingers crossed it's not too bad. Thanks for all the messages."