Second-placed OM trail leaders PSG by nine points, with a vastly inferior goal difference and four games left. A win against Bastia would delay their arch rivals' coronation as champions even if PSG beat Valenciennes on Sunday.
Once again, Marseille will rely primarily on their sturdy defence.
They have not conceded a goal in their last seven league matches and have won 12 of their games by 1-0, equalling PSG's record from 2003/04.
"We have turned the screw," fullback Rod Fanni, who is doubtful because of an ankle injury, told the club's website.
"Let's hope we will continue to hang in there because we have been suffering this year but it has been worth it."
"Not over yet but we'll need an almighty collapse in Paris," OM midfielder Joey Barton said on his Twitter feed.
The PSG players are impatient to win the club's third league title, after 1986 and 1994.
"We need a victory, which we hope to clinch on Sunday so we can be champions at home," Argentine midfielder Javier Pastore told the club's website.
Third-placed Olympique Lyon are on 60 points, four adrift of OM, and, with the title out of their reach, will probably focus more on Saint-Etienne's game against Girondins Bordeaux on Friday.
"If we manage to stay up, which is not done yet, we will leave the Marcel Picot stadium by bicycle and climb the Col de la Schlucht [at the end of a 120-km ride]," president Jacques Rousselot told Reuters.
