Navas suffered the injury in the French champions’ 2-1 win over Atalanta in the quarter-finals on Wednesday and was replaced by Sergio Rico with eleven minutes to go.
The Costa Rican international has played in all but one of PSG’s Champions League games this season but might have to sit out their vital encounter against their German opponents as Thomas Tuchel’s men aim to conquer Europe for the first time in their history.
A statement from PSG on Thursday said: “Keylor Navas left the field during the match on Wednesday evening after feeling some pain in his right hamstring after clearing the ball.
“The examinations and MRI have confirmed a tear in the femoral biceps. His condition will be examined again on Saturday but his involvement in Tuesday's match is uncertain.”
Navas joined PSG from Real Madrid last summer and has so far made 34 appearances in all competitions, winning the Ligue 1 title, Coupe de France and Coupe de la Ligue in his first season in Paris.
The 33-year-old won the Champions League three times during his career at Real Madrid.
PSG will also be boosted by the return of Kylian Mbappe to full fitness after he started from the bench against Atalanta due to an ankle issue, while Angel Di Maria, who missed the game against the Italians due to suspension will be available once again.
