Villarreal defender Angel Lopez is set to be sidelined for around six months after suffering a serious knee injury.
The right-back was carried off on a stretcher during the second half of Sunday's defeat to Real Madrid and the extent of the problem has now been confirmed.
The 29-year-old Spain international has damaged the anterior cruciate ligament in his left knee and is almost certainly out for the rest of the season.
He has already been sent for surgery in Barcelona and will now begin a lengthy rehabilitation process.
Villarreal are third in the Primera Liga standings but are 11 points behind second-placed Madrid following their 4-2 loss at the Bernabeu.