The Catalans face a defensive crisis after Eric Garcia and Jules Kounde were ruled out following their victory over Sevilla.
Gerard Martin is also doubtful after suffering foot discomfort, leaving Flick short of defensive options.
Despite the setbacks, the German tactician remains confident Barcelona can compete against the European champions.
"Frenkie de Jong can play, and Alex Campos is also with us. I am certain everything will go well. Perhaps we are not going through the best moment, but we have to accept that," Flick told the media.
"I think tomorrow's game is a good test for us. I want our team to play with confidence, as a side that has won its last 11 matches does. We will be facing the best team in the world over the last two years, and this is an opportunity for us."