The forward has been hauled off midway through the first half after landing painfully during Barcelona's second-leg cup clash at Getafe.
The Blaugrana were 22 minutes into the second leg in Madrid when the forward first showed signs of pain after landing awkwardly in an attack.
He had to be helped off the pitch - looking in a considerable amount of pain - at the Alfonso Perez, hobbling on his left leg
The Brazil international, 21, was left out of the starting lineup when Gerardo Martino's men faced Atletico Madrid on Saturday, though he came on as a substitute.
This was following a bout of gastroenteritis that kept him out of the first leg of the cup match with Getafe at Camp Nou, which ended 4-0 to the hosts following a double from the returning Lionel Messi.
Lionel Messi scored a double in that clash, which was his return to the Barca team after a lengthy spell on the sidelines, and scored a brace on Thursday as well.