Real Madrid striker Ronaldo is a serious doubt for Sunday's Spanish Primera Liga clash against arch-rivals Barcelona after he pulled up in training on Friday because of pain in his left thigh.
The Brazilian international was thought to be on course to re-appear in the match at the Bernabeu after spending two weeks on the sidelines because of a thigh strain sustained during the 3-0 defeat against Osasuna.
But he was forced to stop training and was examined by club medical staff after feeling pain in his leg as he kicked the ball towards the end of the session.
The club said there was a serious doubt about him playing on Sunday but no decision would be made until the morning of the game.
Ronaldo suffered a similar injury to the same leg last month and was unable to play in the final of the King's Cup against Real Zaragoza, a game Real went on to lose 3-2 in extra time.
Real Madrid are second in the Primera Liga, level on points with leaders Valencia and seven ahead of Barcelona.
Valencia, who lead by virtue of their better head-to-head record against Real, have a tricky away match at fifth-placed Athletic Bilbao on Sunday.