Filipe Luis is set for a spell on the sidelines after suffering a thigh injury during training on Wednesday, Atletico Madrid have announced.
He sat out Tuesday's 1-0 defeat to Bayern Munich in the Champions League with Atleti's progress to the last 16 already secured and a day later he suffered a grade two tear in his left thigh.
Tests conducted on Thursday confirmed the tear, but Atleti did not confirm how long he will be out for.
"Filipe Luis suffered a grade II injury to the semimembranosus muscle in his rear left thigh," a club statement read.
"Our player, who retired from training on Wednesday with discomfort, had medical tests on Thursday at the Majadahonda Clinic.
Atletico look set to be without the 31-year-old for their next LaLiga clash with Villarreal due to the injury.