Marseille, aiming for a record-equalling 10th title, are third in the table, in the Champions League play-off spot, with 49 points from 27 games.
They lie five points behind leaders Paris Saint-Germain, who reached the quarter-finals of the Champions League for the first time in 18 years on Wednesday after a 1-1 home draw against Valencia gave them a 3-2 aggregate win.
PSG have a home game against second-from-bottom Nancy on Saturday, and are three points adrift of Lyon.
"Lyon are a direct rival for the podium. This game is an opportunity to send a message to the teams who are chasing us," Fanni said.
Saint-Etienne, who take a 12-game unbeaten run in all competitions into their match at Stade Rennes on Friday, are two points behind on 47 with fifth-placed Nice, hosts to champions Montpellier (44), on 45.
"We will travel there to get a good result and make amends for the first game," striker Andre-Pierre Gignac told the OM's website referring to last November's 4-1 thrashing at home by Lyon.
"PSG are a class above but they lost at Reims last weekend so anything is possible."
Marseille could rely on Amodou Sougou, who came on as a substitute to set up both goals in the team's 2-1 comeback win against Troyes last weekend.
"I want to go step by step. It's not because I was decisive in the previous game that I should start," Sougou told om.net.
Lyon are not focusing on the table, just on their game.
"It's too soon to look at the standings," defender Samuel Umtiti told the club's website.
"There are a lot of matches left, nothing will be done for second place after this game."
Bottom club Troyes, seven points from safety, on Saturday host 16th-placed Stade Reims who beat PSG last weekend.
"Let's be very careful after that kind of victory," forward Nicolas Fauvergue warned on the club's website.
"If we don't keep our feet on the ground, it could be dramatic."
Safety will be the primary concern, too, when Evian Thonon Gaillard and Sochaux, 18th and 17th respectively, face each other in Annecy on Saturday.
