Paris St Germain are leading the way in the Ligue 1 title battle, with Lyon their closest challengers two points back and Marseille a further three points adrift.
Were Marseille to lose this weekend, they could be eight points off the pace and facing up to their title bid reaching its end.
Manager Elie Baup's team put back-to-back 2-0 defeats by PSG behind them to beat Troyes on Sunday, and need to find a run of positive results to make a serious fight of the championship.
Looking ahead to Sunday's game, Fanni was reported to have told Radio Star by om.net: "Everything is possible. Now I don't like to talk about what might happen in the future because later we could look like imbeciles. But we have everything we need to go there.
"We've shown in Paris, there wasn't much between the teams. So I don't see why we shouldn't be capable of troubling Lyon."
Fanni is confident Marseille are worth at least their current place in the standings.
He said: "Even if our matches aren't always very beautiful and we aren't playing like we'd want, I think that this third place is deserved."