Atletico Madrid have confirmed midfielder Saul Niguez sustained a thigh injury in their Copa del Rey match with Girona on Wednesday.
Diego Simeone's side exited the competition on away goals after drawing 3-3 at the Wanda Metropolitano in the second leg of their last-16 tie.
Saul had to be replaced 11 minutes into the second half and Atleti said a subsequent injury assessment has determined the midfielder has suffered a "high-grade post-traumatic myofascial injury to his thigh".
The club put no timescale on the recovery of Saul, who has started 17 La Liga games for the side second in the table behind Barcelona.