Montpellier visits Rennes in the final match of a rare Monday Ligue 1 schedule, and its lead at the top of the table could vanish before kick off.
PSG, three points back and only one off in goal differential, is the first of three title contenders to play this week, as it visits Valenciennes on Sunday. Ligue 1 does not play Saturday this week.
Defending champion Lille hosts Caen on Monday in a match that kicks off before Montpellier, and could be within two points of the summit with a win.
So, Montpellier - which dropped two points in a 2-2 tie with Evian last week - visits fifth-place Rennes in need of at least a draw to secure its place atop the table for another week.
PSG has also dropped points of late, tying Auxerre and losing to Lille, which has made it a three-team race with a run of four straight wins and seven wins over its last eight matches.
"Two months ago, everybody said we wouldn't even finish in the top five," said Lille coach Rudi Garcia to the Ligue 1 website.
"From that moment on, we said to ourselves that we would no longer look at the table and instead would focus on our own performances, try to play as well as possible and try to position ourselves for the final sprint."
Even though Montpellier remains out of reach this week, Lille could chase down the second spot and PSG, which has struggled down the stretch despite adding well over $100 million in transfers in the summer and winter.
"The objective for the end of the season has not changed and the ambition is still to finish in the top three," Garcia said. "We'll do everything we can to achieve that."
Outside of the top three, who are well clear at the top, fourth-place Lyon has a home match against Brest on Sunday, when it will try to maintain its cushion for the final Europa League place.
Rennes is two points back in fifth place, and St Etienne is three points back in sixth ahead of its home match against Marseille on Monday.
Toulouse, which is five behind Lyon, hosts Nice on Monday and Bordeaux, also still in the Europa hunt, is seven points back ahead of its trip to in-form Auxerre on Monday.
Auxerre has won two straight to climb out of the relegation zone, and will try to continue its ascent.
Sochaux enters this week at the bottom on 33 points and hosts Nancy, and Dijon visits Lorient in need of a win to better its current place in 19th. Brest has to maneuver its visit to Lyon to avoid a drop from 18th.
Also Sunday, 16th-place Ajaccio has just a three-point cushion on the bottom three ahead of its trip to Evian, while Nice is also just three from danger in the relegation battle.