Rafael Marquez also missed the Athletic game with the flu, although he does not have the H1N1 virus.
"If players aren't there ... we'll play with others," said Barca coach Pep Guardiola. "You don't win titles with two or three players. On Tuesday we play Inter and we can't be saying so-and-so is injured or has the flu. The stadium should be full, without an empty seat, and let's get on with it."
Real Madrid took over the top spot in La Liga. Barcelona will be eliminated from the Champions League if it loses at home to Inter Milan and Russia's Rubin Kazan beats Ukraine's Dynamo Kiev.
Barcelona only managed one point in two games against Rubin Kazan, dropping it to third place in Group F with two games to play and losing the tiebreaker to the unfancied Russian club.
Barca's depth will be tested in the next month as it must travel to the United Arab Emirates for the FIFA Club World Cup. It opens play Dec. 16 in Abu Dhabi.