Real Madrid suffered an injury blow to Sergio Ramos in defeat to Cadiz.
Ramos was forced off at half time.
The Real Madrid captain suffered a strong blow to his left knee in the first half and didn't come back out after the break, with Eder Militao taking his spot in the back line.
The substitution was likely made as more of a precaution, but there will be an anxious wait as Ramos goes for further tests to determine if there is an issue there.
Real coach Zinedine Zidane said afterwards: "Let's hope it's nothing major, it's a knock and we'll do what we have to do tomorrow to see exactly what the issue is. Let's hope it's a minor one."
Real meet Barcelona later this week.