Messi played the full 90 minutes of PSG's 2-1 defeat by Marseille in the French Cup on Wednesday and he is in a race against time to be fit for their Champions League last-16 clash with Bayern Munich on Tuesday.
PSG have already lost Kylian Mbappe (23) to injury for two more weeks which means the French forward will play no part in the first leg against the German champions.
"Concerning Kylian, the communication has been made. We talked about an unavailability of three weeks. Kylian is being treated," PSG boss Christophe Galtier (56) told a news conference ahead of Saturday's match against Monaco.
"Leo felt muscle fatigue, he will resume training on Monday. He is not uncertain for Bayern. We know the importance of Leo in our game. In his absence, we'll have to play in a different way with a more solid, more compact team structure.
"Obviously going to Monaco without Leo is always annoying. Injuries happen when there is a sequence of games with a World Cup in the middle of the season. It's up to me to have both a successful team while injecting freshness."
The Argentine World Cup winner has 10 goals and 10 assists in Ligue 1 this season.
However, Galtier confirmed Achraf Hakimi (24) has overcome a hamstring problem and would be available.
PSG are top of Ligue 1 with 54 points from 22 games, eight points ahead of second-placed Marseille. Monaco are fourth with 44 points.