Pogba did not travel with United for Sunday’s 2-1 Premier League defeat at Tottenham, after his father passed away last Friday.
Mourinho does not expect him to be back in time for Wednesday’s trip to St Mary’s Stadium, as he will be attending the funeral.
“I don’t think [he will be available],” he said.
“I think that his dad’s funeral has to be between Tuesday and Wednesday in France.
“I don’t think Paul has conditions to play, we let him be completely free until when he’s ready to be back.”
United will take on Crystal Palace in their last Premier League game of the season, before facing Ajax in the final of the Europa League.