The 29-year-old had to be stretchered off following a challenge from a Saint Etienne player late in the second half.
Neymar had an early goal ruled out by VAR before the hosts took the lead through Denis Bouanga in the 23rd minute but Marquinhos equalised for Mauricio Pochettino’s men on the stroke of half time from a Lionel Messi assist before the former Barcelona captain supplied the balls for Angel Di Maria and Marquinhos again to seal the win in the second half.
The win takes PSG 12 points clear at the top of the Ligue 1 table but they will be sweating on the fitness of their Brazilian superstar.
"Unfortunately, these setbacks are a part of an athlete’s life," Neymar wrote on Instagram after the match.
"Now you have to raise your head and move on. I will come back better and stronger."
Pochettino provided a further assessment of Neymar’s injury after the game.
"For the moment there is nothing to say,” the former Tottenham Hotspurs manager said.
"He felt pain from the twist of his ankle. Tomorrow, he will take exams and we will know a little more about his injury."
Neymar has made 14 appearances in all competitions for PSG this season, scoring three goals and providing three assists.
