The hosts have their work cut out to secure European qualification, while Lorient are at risk of being relegated with a game to spare.
Match preview
Marseille's dreams of lifting their second European trophy were brought to a disappointing end in Thursday's trip to Bergamo.
After playing out a 1-1 draw at the Stade Velodrome, Marseille travelled to Italy with hopes of securing their place in the Europa League final for the first time since 2017-18.
However, those aspirations were quashed by a rampant Atalanta side, with Ademola Lookman, Matteo Ruggeri and El Bilal Toure all getting on the scoresheet to condemn Les Phoceens to a heavy 3-0 defeat.
While Atalanta will go on to face Bayer Leverkusen in the final, Jean-Louis Gasset's side will now turn their focus to their final three league games against Lorient, Reims and Le Havre as they look to secure European qualification for next season.
Having collected 44 points from 31 matches, Marseille are sitting in ninth place and five points adrift of sixth-placed Lens, who they beat 2-1 in their most recent Ligue 1 outing to end a five-game winless run in the top flight.
Although they have a game in hand over the three teams above them, Les Phoceens know they can ill afford to drop points in their final three matches, beginning with Sunday's home contest against a Lorient side they have beaten in eight of their previous nine head-to-head meetings.
Lorient are in a perilous position after losing each of their last six matches, including their recent 2-0 defeat to European hopefuls Lens.
Having failed to win any of their last eight matches, Les Merlus are languishing in 17th place with just 26 points and six points adrift from 15th-placed Le Havre.
With Le Havre boasting a sizeable goal difference advantage, Lorient's best hope of surviving is to close the three-point gap to Metz in the relegation playoff spot.
However, their four-year stay in the top flight will come to an end if they fail to match Metz's result, with their relegation rivals set to travel to Stade de la Meinau for a meeting with Strasbourg.
Having shipped 63 goals in 32 matches, Lorient currently have the worst defensive record in the top flight, and while their vulnerable backline will be an obvious concern ahead of Sunday's contest, they will also need to improve at the opposite end of the pitch after failing to score in any of their last three games.
The size of Lorient's tasks is demonstrated by the fact they have failed to win any of their last 11 meetings with Marseille since they scored two late goals to claim a dramatic 5-3 victory at the Stade Velodrome in April 2015.
Marseille Ligue 1 form:
L
L
L
D
D
W
Marseille form (all competitions):
W
D
D
W
D
L
Lorient Ligue 1 form:
L
L
L
L
L
L
Team News
Marseille remain without midfielder Valentin Rongier and forward Bilal Nadir due to knee injuries, while defender Leonardo Balerdi is set to serve a one-match suspension for an accumulation of yellow cards.
With Balerdi unavailable for selection, Amir Murillo could be given the chance to feature in a back three alongside Chancel Mbemba and Samuel Gigot.
Ulisses Garcia, Jean Onana and Pape Gueye were forced to miss the two games against Atalanta after they were omitted from Marseille's Europa League squad by Gasset's predecessor Gennaro Gattuso, but the trio are expected to return to the matchday squad for Sunday's Ligue 1 fixture fixture.
As for the visitors, they may have to cope without the services of Igor Silva, Ayman Kari, Bonke Innocent, Quentin Boisgard, Formose Mendy and Bamba Dieng.
Lorient boss Regis Le Bris could be tempted to recall Isaak Toure to operate in a back three with Montassar Talbi and Nathaniel Adjei.
Mohamed Bamba will continue to lead the line after scoring seven goals in 14 matches since arriving from Austrian side Wolfsberger in January.
Marseille possible starting lineup:
Lopez; Murillo, Mbemba, Gigot; Clauss, Veretout, Gueye, Onana, Garcia; Harit, Ndiaye; Aubameyang
Lorient possible starting lineup:
Mvogo; Adjei, Talbi, Toure; Katseris, Abergel, Bakayoko, Mendy; Louza, Ponceau; Bamba