Cristiano Ronaldo was left "worried" by the sprained ankle he suffered in Sunday's 2-2 Clasico draw with Barcelona, but Real Madrid are hopeful it's not serious, manager Zinedine Zidane said.
The Portuguese star had pulled Madrid level with a goal from close range in the 14th minute, but in the process he was clattered into from behind by Barcelona defender Gerard Pique.
Ronaldo limped to the sideline, and though he returned after receiving treatment to see out the end of the first half -- and nearly scored a second goal -- he was substituted at half-time.
Real Madrid told reporters during the game that Ronaldo had suffered a slight ankle sprain in an initial diagnosis, but with the Champions League final less than three weeks away, Zidane was unable to completely calm fears.
"I cannot say how long he will be out," Zidane said after the draw. "Cristiano does not feel good, but he says it's only a small problem.
"We will see tomorrow, with the tests, and do what we need to see how his ankle is. He is a bit worried, as the ankle is a bit swollen, but he says it is not so much."
There was not much at stake in the Clasico, with Barcelona having already secured the title in La Liga. And while Real are trying to catch city rivals Atletico Madrid for second place, the focus must be on the Champions League final against Liverpool on May 26.
Ronaldo also has to consider his fitness ahead of the World Cup, with Portugal set to kick off against neighbours Spain on June 15.
Marco Asensio came on to replace Ronaldo at the second half of Sunday's match, but though Barcelona were down to 10 men following a red card to Sergi Roberto, the hosts soon took the lead through Lionel Messi's strike in the 53rd minute.
However, Gareth Bale netted an equaliser in the 72nd minute to salvage a draw and pull Real within three points of Atletico with a game still in hand.