Having lost all three games in the competition so far, Les Olympiens are rock-bottom in Group C, and another defeat on Wednesday would effectively spell the end of their campaign.
The route to Europa League football is also looking difficult, as Olympiacos are already three points ahead of them and Andre Villas-Boas' side face Manchester City at the Etihad on the final matchday.
Porto, meanwhile, have recovered well since the opening day loss to the Skyblues, winning the next two games with a combined score of 5-0. The Portuguese side look primed to progress through the group on the coattails of the Premier League giants.
Marseille vs Porto Head-To-Head
Porto have a clear advantage in this fixture historically, winning four out of their five games against Marseille, including a 3-0 thrashing at the Estádio do Dragão three weeks ago.
The only stalemate played out between these sides came at the venue of this upcoming clash, as Marseille held them to a 1-1 draw back in October 2007.
Marseille Form Guide (all competitions): L-W-L-L-W
Porto Form Guide (all competitions): W-L-W-W-W
Marseille vs Porto Team News
Marseille should have Hiroki Sakai and Alvaro Gonzalez back in the lineup after they sat out of the weekend's game against Strasbourg in Ligue 1. The French side do not have any fresh injury concerns.
Porto are facing a defensive crisis, with goalkeeper Mouhamed Mbaye and centre-back duo Pepe and Ivan Marcano all out injured. Right-back Jordan Amavi is already on two yellow cards and will be suspended for the Olympiacos game if he goes into the book again on Wednesday.
Injured: Mouhamed Mbaye, Pepe, and Ivan Marcano.
Marseille vs Porto Predicted XI
Marseille (4-1-2-1-2): Steve Mandanda; Hiroki Sakai, Alvaro Gonzalez, Duje Caleta-Car, Jordan Amavi; Boubacar Kamara; Valentin Rongier, Morgan Sanson; Dmitri Payet; Florian Thauvin, Dario Benedetto.
Porto (4-4-2): Agustin Marchesin; Wilson Manafa, Chencel Mbemba, Malang Sarr, Zaidu Sanusi; Jesus Corona, Sergio Oliviera, Mateus Uribe, Otavio; Moussa Marega, Luis Diaz.
Marseille vs Porto Prediction
Porto may have cruised to a victory against Marseille in the reverse fixture, but their record away from home in Europe has been poor recently, losing four of their last five games on the road.
This might give the French outfit a boost, allowing them to pick up their first European point of the season.
Prediction: Marseille 1-1 Porto