The Brazilian came off in the first half of the Blaugrana's victory over Granada with a knee issue and will undergo further tests.
Rafinha suffered a meniscus injury to his right knee in Barcelona's match against Granada, the club have confirmed.
The Brazilian was named in the starting line-up for the Liga clash at the Nuevo Los Carmenes, where Luis Enrique's title-holders were without the suspended Lionel Messi.
The absence of the Argentina star saw Rafinha, who also started the 4-2 victory at home to Valencia before the international break, deployed in a more advanced role.