Star striker Robert Lewandowski is a doubt for Bayern Munich's Champions League quarter-final clash with Real Madrid on Wednesday after he only trained for 20 minutes because of a bruised shoulder.

Lewandowski has scored 38 goals this season, including seven in the Champions League, and is crucial to Bayern's chances in the first leg at the Allianz Arena.

He injured his right shoulder on Saturday when he netted twice in Bayern's 4-1 thrashing of Borussia Dortmund.

Lewandowski said afterwards he was confident of facing Real, but his struggles in training on the eve of the match suggest he faces a battle to be ready.

"He trained today only for 20 minutes because he had a problem in his last game. He felt good, but we'll see how he feels tomorrow," coach Carlo Ancelotti told a press conference on Tuesday.

"If he has no pain he will play, if he has pain, he won't play."

Ancelotti refused to be pressed when asked what the chances are of Lewandowski facing a Real side led by their superstar forward Cristiano Ronaldo.

"I can't give a percentage, he trained today and we have to see how he feels," said the Italian.

"He had a good feeling but I can't say whether he will feel better or not (tomorrow)."

If the Polish predator drops out his forward place is likely to go to Thomas Mueller, who netted twice in the 6-0 drubbing of Augsburg a fortnight ago but has missed the last two games with an ankle injury and has struggled for form this season.

"If he (Lewandowski) doesn't play, it won't affect our preparations and plans," said Ancelotti.

"We know how important Lewandowski is to us but we also have other good players."

Winger Arjen Robben said the German champions were not nervous about the prospect of losing their star goalscorer.

"The advantage we have is that we have a big team at our disposal, if he doesn't play -- which isn't sure yet -- we have other players who can step in, which is why we are calm about it," said the Dutchman, who spent two years at Madrid before joining Bayern in 2009.

Real coach Zinedine Zidane assumes Lewandowski will play.

"We are preparing to face him. If he doesn't play Bayern have other good players in other positions and I'm sure whoever replaces him will play well," said Zidane.

Real's Germany midfielder Toni Kroos hopes Lewandowski is fit to play.

"To be honest, I'd be happy if he plays," said the attacking midfielder.

"I'd be happy if both teams had their best players out (on the pitch). I think Bayern will play with their strongest team and I like a challenge."

Bayern goalkeeper Manuel Neuer will be back between the posts after missing the last two games having had minor foot surgery.

"Neuer is fit, he trained well today and he will start the game," confirmed Ancelotti.

Bayern will definitely be without Germany centre-back Mats Hummels, who injured ankle ligaments in training on Sunday and is doubtful for the return leg on April 18.

In Hummels' absence Jerome Boateng and Javi Martinez will partner up at centre-back for Bayern, who are bidding to reach the semi-finals for the sixth year in a row.