Real Madrid will be without Gareth Bale as they look to book their place in a record seventh straight Champions League semi-final against Bayern Munich on Tuesday.
Bale is sidelined by the recurrence of an ankle problem picked up in Madrid's 2-1 first-leg win last week and is also a doubt for Real's crunch La Liga clash with Barcelona on Sunday.
The Welshman was sidelined for three months earlier in the season after suffering ligament damage in his right ankle.
"Gareth worked very hard to get back into the team after his injury," said Madrid coach Zinedine Zidane on Monday.
"When he came back he was desperate to be involved and now he has a small niggle that is preventing him from being fully fit.
"I hope it is nothing and in a few days he can be with us again.
"He won't be fit for Bayern because we don't want to take any risks."
Bale missed Real's 3-2 win at Sporting Gijon on Saturday and Zidane was far from confident he will be fit in time to face Barca.
"I hope he will be with us, but we have to wait and see," he added. "It is a question of taking it day by day."
By contrast, Bayern look set to be handed a huge injury boost as top scorer Robert Lewandowski returns after a shoulder injury.
"We know how good a player Lewandowski is, he is a true number nine," added Zidane.
"That is a plus for Bayern, but he is their player.
"They have good players in all positions and we have to concentrate on our own game."
Lewandowski has scored 38 goals in 40 appearances this season and his presence was badly missed as Bayern not only slumped to defeat at home last Wednesday, but also drew a blank in a 0-0 draw at Bayer Leverkusen on
The Pole has also shown he is capable of the spectacular against Madrid -- he scored all four of Borussia Dortmund's goals in a 4-1 semi-final, first-leg rout back in 2013.
"Lewandowski is a quality player but it's not all about him," added Madrid midfielder Casemiro.
"They've got a brilliant squad.
Madrid have never failed to progress after winning the first leg away from home in the Champions League.
However, Zidane insisted the 11-time European champions were not assured of anything despite having the advantage thanks to Cristiano Ronaldo's second-half double at the Allianz Arena.
"We can't think about the first leg, that has already gone," said Zidane.
"We know the difficulty we face. Whether Bayern play at home or away they don't change how they play.
"We still have a game to play and we need to play very, very well."
Both sides have defensive concerns with Madrid definitely without centre-backs Raphael Varane and Pepe through injury.
Bayern's preferred centre-back duo Jerome Boateng and Mats Hummels face a race against time to be fit, while Javi Martinez is suspended after being sent-off in the first leg.