The Brazilian, who had already missed two previous matches with a thigh injury, felt pain in the same leg during PSG's victory at Valenciennes on Wednesday and had to be replaced at halftime.
PSG, second in Ligue 1 with 15 points from seven games, two behind leaders Monaco, host the Portuguese side on Wednesday in a Champions League clash between the two Group C favourites.
Brazilian centre back Marquinhos, who joined from AS Roma in July, and Frenchman Zoumana Camara are the only centre backs available for Saturday's game. Captain Thiago Silva has been ruled out for six weeks.
"We're a bit short (of centre backs). The thing is that you often have injuries in the same line. We have to deal with it, but it has to stop otherwise it will really be a problem," Blanc said.