"I can't say if he'll be back for the match on Sunday," Blanc told a news conference in quotes posted on the club website (www.psg.fr).
The Uruguayan daily El Observador said on its website (www.elobservador.com.uy) the 26-year-old Uruguay striker had been sorting out divorce issues in Montevideo on Friday.
Cavani, who has scored 12 league goals in France since his French record $84 million transfer from Napoli, left for Montevideo after scoring twice to help PSG beat St Etienne 2-1 at home on Wednesday to reach the French League Cup quarter-finals.
(Reporting by Rex Gowar in Buenos Aires; Editing by Ian Ransom)
