Bayern Munich defender Raphael Guerreiro is doubtful for next week's Champions League semi-final return leg at Real Madrid after he picked up an injury in their 3-1 loss to Stuttgart on Saturday, head coach Thomas Tuchel has said.

Bayern, who also had Eric Dier taken off at half-time with a head injury, face Real in Spain on Wednesday after their 2-2 draw in Munich earlier this week.

Portugal international Guerreiro was taken off in the 17th minute after he hurt his ankle in an attempt to block a shot.

"Raphael Guerreiro needed crutches to walk. It is very, very bitter for us. He was supposed to get some playing time today to be ready for Wednesday. Instead, now we have to see what happens," Tuchel told reporters.

"Eric Dier had to get stitches to the head wound that then opened up again so we at some point said it was enough. We did not want to risk it."

Bayern have several injury concerns, with defender Matthijs De Ligt still doing individual training and fellow defender Dayot Upamecano, who came on for Dier, working back to full fitness after recovering from injury.

"If there ever was a day when we needed to put this behind us quickly then it is today, and we see what we need for Wednesday," Tuchel said.

"The medical meetings at the moment are more maths than medical. Who is on 60 per cent, who on 30 per cent, who can't play at all," said the coach, who will leave at the end of the season following a disappointing domestic run.

Bayern are second in the league, two points ahead of Stuttgart in third and with two games left to play. The title has already been wrapped up by leaders Bayer Leverkusen.