Alex Sandro suffered a thigh strain in the Italian Supercoppa defeat to AC Milan, Juventus confirmed on Saturday.
Sandro left Friday's game in Doha, Qatar, in the 33rd minute before Milan went on to win on penalties.
"Initial medical tests have shown that Alex Sandro strained the flexor muscles in his right thigh," a Juventus statement said.
"The Brazilian full-back's condition will continue to be closely monitored over the coming days."
Reports from Italy said Sandro faces about three weeks out, though the team's next game is not until Jan. 8.
Sandro joins Leonardo Bonucci and Dani Alves on Juventus' injury list.