Kylian Mbappe left Paris Saint-Germain's Ligue 1 match with Lyon due to injury after 70 minutes.
Mbappe had scored PSG's first and fourth goals as they cruised into a 4-1 advantage against one of their title rivals.
However, as he chased a hat-trick, he was forced off, with Neymar making his return from injury by coming on.
What happened to Mbappe?
Mbappe was seeking his third goal of what had up until that point been very successful.
Coming in from the left wing, he tried a powerful shot that Anthony Lopes in the Lyon goal saved. In landing after his effort, however, the France international immediately signalled that he wanted to come off.
Neymar quickly got himself stripped and ready for action. Mbappe walked off the field unaided, which would seem to suggest that his issue is not a particularly serious one.
What's been said?
Head coach Mauricio Pochettino has played down the issue.
"Kylian came off as a precaution. He received a blow. He twisted his ankle in the first half," he said.
What games will Mbappe miss?
Until there is a scan, it is impossible to know how long Mbappe will be out for.
Given the striker's reaction on the bench, however, it is unlikely to be a lengthy absence. He is a doubt to feature in France's forthcoming World Cup qualifiers against Ukraine at home then Kazakhstan and Bosnia and Herzegovina away.
PSG, meanwhile, face a huge week following the international break. They face fellow Ligue 1 title rivals Lille at home on April 3 then tackle Bayern Munich away on April 7. It would be a major blow if he were to miss these games.
The slight silver lining to Mbappe's injury is that Neymar was able to make his return from injury. The Brazil international had missed nine successive games.