The club captain missed their Bundesliga match against Bayer Leverkusen with a thumb injury and is unlikely to feature this week against Hertha Berlin.
Liverpool host the German champions in the first leg of their last 16 tie on Tuesday 19 February.
The German club announced that Neuer suffered “blemish on the right hand” during a training session and will be x-rayed to assess further damage.
Sven Ulreich played his league game of the season in Neuer’s place and revealed his teammate was missing with a thumb strain, a condition that could mean there is ligament damage.
“The thumb [Neuer's] is really fat, but in one or two days things should look different and he could be able to play,' said Ulreich, after Bayern’s 3-1 defeat on Saturday.
“Of course, I was happy to be able to play again, but it was bitter news for Manuel.”
Neuer could face up to three months out if the ligament in his thumb is torn, which would rule him out of both legs against Liverpool as well as a crucial run of games in Bayern’s attempt to salvage a poor season as they continue to struggle in third.
Manager Niko Kovac, who is coming under increasing pressure at Bayern Munich, said that the club are still in the dark over Neuer’s injury. “I can not say exactly. When I say it will be five months, there is a big fuss, and if I say it will be five days, everyone thinks it’s not that bad,” he said after the weekend defeat.
“The fact is, he was in pain. Otherwise, he would have played.”
Virgil Van Dijk is suspended for the first leg after accumulating three yellow cards in the group stage. Joe Gomez will also miss out after it was announced that he will undergo surgery on a leg fracture.
“It’s a blow for the boy and for us – because prior to the injury he was in such fantastic shape,” said Klopp on Gomez’s injury.
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