Having both booked their places in the French League Cup final in mid-week, Marseille and Lyon meet on Sunday for a dress rehearsal that could have significant bearing on the battle for Champions League qualification.
Marseille, who beat neighbours Nice 2-1 on Wednesday, are France's form team with eight consecutive victories in all competitions behind them.
They are now up to fifth in the Ligue 1 table, just two points below the Champions League places, and a win over fourth-placed Lyon at Stade Velodrome would lift them above Remi Garde's side in the standings.
Victory over Nice came at a cost, however, with Mathieu Valbuena sent off after being shown a harsh second yellow card for taking a free-kick before the official had blown his whistle.
Valbuena, who tops the league's assists chart with 11 decisive passes, has been a key figure in OM's winter revival and team-mate Alou Diarra was left to rue the suspension that has ruled the diminutive midfielder out of Sunday's game.
"It's the first time I've seen a red card like that," said Diarra.
"We're losing an important player who's in form for a free-kick that was taken too quickly. I find that stupid."
Valbuena's absence gives Didier Deschamps further problems as the OM coach was already missing Ghanaian brothers Andre and Jordan Ayew due to their participation at the Africa Cup of Nations, as well as injured pair Stephane Mbia (thigh) and Andre-Pierre Gignac (groin).
Sunday's game will also be the first since Argentine midfielder Lucho Gonzalez returned to former club Porto on transfer deadline day, while Morgan Amalfitano complained of pain in his shoulder on Wednesday evening.
Souleymane Diawara and Charles Kabore have, however, both returned from Africa Cup of Nations duty and Deschamps will be glad of their presence against a team who showed great heart to fight back from two goals down to beat Lorient 4-2 in their League Cup semi-final on Tuesday.
"Lyon are a team like us, who are still involved in four competitions," said Deschamps. "I watched their match yesterday (Tuesday). They have quality, talent and mental strength. It'll be a top-level contest on Sunday night."
Lyon won the reverse fixture 2-0 in September but lost 1-0 at Montpellier last month in their most recent fixture against a fellow Champions League candidate.
Third-placed Lille are visiting second-bottom Sochaux.
Reigning champions Lille are seven points behind PSG in third place but on-loan midfielder Joe Cole has not given up on the title yet.
"I think that Lille can be champions," he told Thursday's L'Equipe.
"Looking at it from a distance, like everyone, I'd say that Paris will be champions. But I think that we can fight."
Paris Saint Germain survived the big chill in France with their lead at the top of the ligue intact after a 3-1 win over Evian at the Parc des Princes on Saturday although Montpellier kept in touch with a 1-0 success over Brest.
Elsewhere, Dijon slid to a 2-1 home loss to Valenciennes and Ajaccio were held 1-1 by Nice - but the Corsican hosts remain out of the drop zone after a strong recent run including four straight wins.
Nice themselves are in the bottom three along with Auxerre and Sochaux, three points further back.
The match between Saint-Etienne and Lorient fell victim to the cold snap.
Fixtures
Sunday (1600GMT unless otherwise stated):
Caen v Auxerre, Sochaux v Lille, Marseille v Lyon (2000GMT)
Source: AFP
