Rafinha's season is almost certainly done, unfortunately, according to Diario SPORT. The Brazilian suffered a serious injury in Barcelona's 1-1 draw with Atlético Madrid. Despite this, he kept playing and finished the match. He felt pain but he was unaware of the extent of the injury. However, tests later revealed he had torn the anterior cruciate ligament in his left knee.
The Brazilian will require surgery, and it's very unlikely he'll be back in playing shape before the end of the current season. Rafinha had just come back from a long injury layoff in December 2017.