"Sergio Busquets and Eric Abidal will not feature in tomorrow's match," Barca said in a statement on their website on Tuesday.
"The midfielder has not recovered from the [groin] injury that kept him from playing... this weekend, while the Frenchman has picked up a calf injury," they added.
Busquets is a crucial part of the Barca side in the often unsung defensive midfield role and without him their chances of overturning a 4-0 deficit from last week's first leg in Munich are severely dented.
The Spain international missed Saturday's 2-2 La Liga draw at Athletic Bilbao, when his place was taken by Alex Song. The Cameroon international turned in a decent performance but in general has struggled to make his mark since joining from Arsenal at the end of last season.
Barca's hopes of making next month's final at London's Wembley Stadium and winning a third Champions League crown in five years appear remote after they were comprehensively outplayed by the German champions in the first leg.
"We are Barca and we cannot give up on a tie, there are still 90 minutes left," coach Tito Vilanova told a news conference.
"I don't think Bayern believe it is over either though they are better off than we are," he added.
"If we lose, at least we have to do it with our heads held high and playing on until the end of the match, not throwing in the towel and making our fans proud of us."
