كتب : Omar AbdelAziz
Beckham and Reyes were taken off injured in Real's Spanish league draw with Getafe on Sunday.
Real manager Fabio Capello confirmed the absence of both players from the match speaking after the Getafe game.
"Neither of them will play in Germany," Capello said in a press conference on Sunday.
"One of the injuries is serious and the other could be something important. We will have to see."
Beckham crashed into the advertising boards behind the goal when attempting a byline cross and limped off before being substituted in the 68th minute.
On-loan forward Reyes also injured his left knee after colliding with the Getafe keeper and was carried off on a stretcher after 35 minutes to add to Capello's worries before the Bayern game.
Capello will also have to wait on the fitness of Gonzalo Higuain who was the third player to be taken off during the Getafe game with a knock late in the second half.
"Higuain could also be seriously injured, but we will have to wait until tomorrow to determine this," added the Real Madrid boss.
Despite winning the first-leg against Bayern Munich 3-2 at the Bernabeu, Real Madrid seem to be the ones with a tougher task in Wednesday’s clash.
Bayern only need a one-goal victory over the Spanish giants to secure passage to the quarter-finals.