Neymar may miss Paris Saint-Germain's next few matches after limping off in Wednesday's Champions League win over Istanbul Basaksehir, Thomas Tuchel revealed after the game.
PSG have three matches in the next 10 days - against Nantes and Rennes in Ligue 1, either side of a trip to RB Leipzig in the Champions League - before the international break.
And Tuchel is worried Neymar, who has two goals and three assists in six appearances this term, will not play a part in any of those games.
"It was necessary to take him off," Tuchel told RMC Sport . "We now have to wait for a diagnosis. It was not serious pain, but he felt uncomfortable.
"Because of the tight schedule, it might cost him a few games, though I cannot be sure at this point."
Asked for a further update at his news conference, Tuchel said: "It is the adductor muscle. I hope it's not too bad an injury. We have to wait for the tests tomorrow."
Despite the early exit of Neymar, PSG earned a 2-0 win through Moise Kean's second-half brace as they recovered from last week's Group H defeat to Manchester United.
Last season's beaten finalists produced a largely laboured display and Tuchel, who has had to fend off repeated questions over his future, admits an improvement is needed.
"We won - that's what we wanted to do," he said. "We know we will have to improve. Some things have been good for us, other things not. We play every three days, so we'll have time to work on that for the next few matches.
"We know we can play better, but we have to accept that we can't do it right now. It's more difficult but I want to protect my players because I think they are doing the maximum.
"We knew we were going to fall against a team that was going to put aggression in the game.
"It's true that we may have lacked communication in the first half. We corrected that in the second and won the game."
PSG managed only one attempt on target in the first half and were indebted to Kean for their victory.
The forward became the youngest ever Italian player to score on his first Champions League start at 20 years and 243 days, overtaking Alessandro Del Piero's record.
"This will give me the strength to continue working hard," said Kean, who has four goals in four appearances since joining on loan from Everton.
"It has been a good start. I have to be ready for my team-mates and be ready when called upon."
PSG have now found the net in 36 of their last 37 matches in all European competitions, the exception being August's Champions League final defeat to Bayern Munich.