Alex, who joined PSG from Premier League Chelsea during the January transfer window, missed last weekend's 3-1 defeat of Evian Thonon Gaillard with a calf injury.
"We know it's always a tough game, playing Nice at their Stade du Ray, but we're not going to let go of anything," said striker Kevin Gameiro.
Second-placed Montpellier, who trail PSG by three points, take on AC Ajaccio on Saturday and will leapfrog the leaders on goal difference if they win and the Parisians lose.
Olympique Lyon, with France playmaker Yoann Gourcuff still expected to be on the bench, entertain Caen on Saturday.
Gourcuff, who has made only seven Ligue 1 appearances this season and has not featured for France in almost a year, played in Lyon's 3-1 extra-time French Cup quarter-final win over Girondins Bordeaux on Wednesday but was replaced midway through the second half having looked far from his brilliant best.
"He is very close [to playing more regularly]," coach Remi Garde told French radio RMC this week.
"He had a minor knee injury [earlier this season] but he is getting close to the level that will allow him to play more," said Garde. "It's a team sport, so we need everybody."
Lyon, whose game is one of six brought forward to 14:00 GMT because of the cold weather, are fourth in the standings with 39 point from 22 games, 10 points adrift of PSG.
Fifth-placed Olympique Marseille, 11 points off the pace, will be looking to stay close to champions Lille, who are in third place, the last Champions League qualifying spot.
Lille, who were knocked out of the French Cup on Wednesday, have a game in hand and are one point ahead of Marseille before they host improving Girondins Bordeaux on Sunday.
