The France winger has returned to training ahead of the resumption of the Bundesliga season after missing friendlies against Al Kuwait and Red Bull Salzburg.
However, Bayern coach Guardiola revealed the former Marseille man is an injury concern for the trip to third-placed Gladbach.
"He was in pain in the legs in the last days. Today we have the last training, until now I still do not know whether he can play tomorrow," said the Spaniard.
"He is one of the best players in the league in recent years. We need him, it is a pity for us and for him that he has been able to play so little," the former Barcelona coach said.
Guardiola is expecting a stern test from Lucien Favre's side, who are unbeaten in eight league games.
"If we don't put all of the things that set us apart into action, then we will have problems," he added.
