Les Phoceens have won their last six matches and enter the midweek round of fixtures two points off top spot, while Rennes are five points worse off in eighth.
Marseille's Champions League campaign may not have gone to plan, finishing bottom of Group C with just three points from a possible 18, but they are looking good domestically.
Andre Villas-Boas's side battled to a 2-1 win over Monaco at the weekend and are firmly in the title race, which was blown wide open by Paris Saint-Germain's latest slip-up.
The reigning champions lost 1-0 to Lyon on Sunday and now just three points separate the top five sides.
Marseille are currently fourth, though they do still have two games in hand on each of the sides above them and could move four points clear if they win both.
The visitors' run of six successive wins is the best current run of any side in Europe's top five leagues, though not since October 2014 have they won seven in a row.
Rennes beat Nice 1-0 last time out through M'Baye Niang's first-half goal, but they have lost their last two home matches without scoring - not since May 2013 have they lost more consecutive matches at Roazhon Park
Les Rennais have won only one of their last 12 home league games against Wednesday's opponents, however, with that solitary victory coming in September 2016.
Marseille have been impressive on their travels, too, going 14 without defeat, which is again the current longest streak in the top European leagues.
Rennes Ligue 1 form: WLLDLW
Rennes form (all competitions): LDLLLW
Marseille Ligue 1 form: WWWWWW
Marseille form (all competitions): LWWWLW
However, Gomis's deputy Romain Salin has saved 72.7% of the shots he faced in Ligue 1 this season, compared to a 60% return for Gomis.
In-form striker Dario Benedetto seems certain to start again as he looks to become the first Marseille player to score in four consecutive games in the top flight since Bafetimbi Gomis in December 2016.
Rennes possible starting lineup:
Salin; Traore, Silva, Aguerd, Maoussa; Nzonzi; Doku, Camavinga, Grenier, Truffert; Niang
Marseille possible starting lineup:
Mandanda; Sakai, Gonzalez, Caleta-Car, Nagatomo; Rongier, Kamara, Gueye; Cuisance; Thauvin, Benedetto
We say: Rennes 1-2 Marseille
Both sides are now focusing on domestic matters after exiting the Champions League with a whimper.
Whereas Rennes have been pretty inconsistent in Ligue 1 so far, Marseille are Europe's form side right now and should have enough to pick up three more points on Wednesday.