Neymar was forced off injured with a sprained ankle in the first half of Barcelona's Copa del Rey clash with Getafe on Thursday.
The Blaugrana were 22 minutes into the second leg of the last 16 in Madrid when the forward landed painfully after crossing the ball for an attack.
Neymar had to be helped off the pitch - looking in a considerable amount of pain - at the Alfonso Perez, hobbling on his left leg with assistance from Barca medical staff.
The Brazil international, 21, was left out of the starting line-up 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.
Lionel Messi scored a double in that clash, which was his return to the Barca team after a lengthy spell on the sidelines, and opened the scoring on the brink of halftime on Thursday following Neymar's injury.