Alves and Busquets were both substituted during the 1-0 win at San Mames and underwent tests on Monday morning.
The club announced in a statement on their official website that Alves had suffered a groin injury but gave no indication of how long the Brazilian is likely to be sidelined.
The statement also said that Busquets
“suffered a slight ankle injury but nothing important,”
suggesting he is expected to be available for Saturday’s game at home to Malaga.
Speaking after the win over Athletic, Barca boss Luis Enrique had said:
“This is a contact sport and we are not having much luck, although they do not seem to be serious injuries.
“The preseason meant we had to compete very quickly, and there are more risks that this could happen.”
Midfielder Sergi Roberto came on as a replacement for Alves at right-back, with summer signing Aleix Vidal not permitted to play for the club until January due to the FIFA transfer ban.