Real Madrid left-back Marcelo was forced off through injury as Los Blancos beat Real Betis 5-3 in La Liga on Sunday, and it is feared the Brazil international's problem could be "really, really bad."
He went down clutching his hamstring in the 26th minute and was replaced by Theo Hernandez after failing to walk off the knock.
Per AS, Real's director of institutional relations, Emilio Butragueno, did not give a positive update on Marcelo's condition after the frenetic encounter at the Estadio Benito Villamarin: "We need to wait and see what the doctors say. He's had to leave the pitch, and it's really, really bad news. In 48 hours we'll know the exact extent of the injury."
Los Blancos manager Zinedine Zidane, though, was more optimistic, per AS: "Hopefully Marcelo's [injury] isn't much. We'll see tomorrow. He's said that he feels it isn't much, but we'll see over the coming days."
Zidane's side were trailing 2-1 at half-time against Betis, but second-half goals from Sergio Ramos, Marco Asensio, Cristiano Ronaldo and Karim Benzema saw them to a crucial victory.
Though the league title is out of reach—they are 17 points behind leaders Barcelona—Real sit in fourth, six points ahead of fifth-place Sevilla with a game in hand.
Barring any major disasters, Real should be able to secure a top-four finish in La Liga, an accomplishment that has looked under threat at times during a challenging domestic campaign.
As a result, Real's main focus for the remainder of 2017-18 is to attempt to win the UEFA Champions League for the third season running.
The Madrid giants have a 3-1 lead over Paris Saint-Germain from the first leg of their last-16 tie, but Zidane will still want his best side available for the second leg on March 6.
That side includes Marcelo, who has been one of Real's most consistent performers while they have enjoyed huge success in recent campaigns.
Quality cover for the 29-year-old is somewhat lacking in Zidane's squad.
Real can likely navigate their upcoming Liga matches against Leganes, Alaves, Espanyol and Getafe without Marcelo, but they will want him back to face PSG.