Ivory Coast international Toure and Hleb of Belarus were suffering from leg muscle strains and missed the league leaders' 1-0 win over Real Valladolid on Saturday.
Hleb is unlikely to be in coach Pep Guardiola's starting line-up but defensive midfielder Toure could be an important factor in stopping Bayern playmaker Franck Ribery.
Guardiola singled out the Frenchman and Italian striker Luca Toni as a key threat to the Catalans' hopes of progressing to the semi-finals, where they would play Liverpool or Chelsea.
"Ribery is a player with a big personality and great all-round ability," Guardiola said at a news conference at the Nou Camp.
"Toni is a different kind of player, very intelligent and particularly dangerous in the penalty area," added the former Barcelona and Spain midfielder, who played with Toni during a stint at Italian club Brescia.
Guardiola suggested Bayern had a small advantage in being able to play the second leg of the last eight tie at home on April 14 and said his side would be aiming to attack the Germans from the start of Wednesday's clash.
"We will play the ball around as usual and try to create rhythm and tempo and make it difficult for Bayern to get the ball," he said.
"We are going to have to be at our very highest level to score goals and we know that at this level your mistakes are punished ruthlessly, especially against a team like Bayern."
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