The Argentina forward was taken off on a stretcher in the second half of Atletico's 2-1 win at Athletic Bilbao on Saturday after a crunching challenge from Carlos Gurpegi.
Club doctor Jose Maria Villalon told a news conference on Sunday the injury was not as serious as feared and Aguero would undergo intensive therapy and take anti-inflammatories in the race to be fit.
"It's not a serious injury," Villalon said, adding that the 22-year-old had suffered only bruising.
"It's very difficult but we'll intensify the therapy so he can recover (in time for the Barca match)."
Aguero was in sparkling form on Saturday, helping to set up Diego Forlan for Atletico's first goal, and was a constant threat with his skilful runs and creativity.
Atletico were the only team to beat Barca last season and top the standings with two wins from two matches, ahead of Valencia on goal difference.
