Benoit Cheyrou believes Marseille need to bounce back from their 2-0 Europa League defeat by Borussia Monchengladbach against Lyon.
Marseille trail leaders Paris St Germain on goal difference and stand a single point ahead of visitors Lyon in the table.
With Marseille and Lyon both in qualifying places for next season's Champions League there is more than just their Ligue 1 title chances at stake at the Stade Velodrome.
Cheyrou told the club's official website: "Of course, we took a blow to the head, but we must quickly prepare for the match with Lyon.
"We must recover, it will affect our physical and mental strength, but we must work hard."
OM also last to Troyes in their last league game and Cheyrou continued: "That's two defeats in a row against teams it was within our reach to beat.
"We are now focused on the big match which awaits us on Sunday. You have to recover well so you can play at your best."
Marseille will use the occasion to launch a new black and pink kit aimed at raising awareness and funds for the fight against female cancer.
Lyon coach Remi Garde does not believe facing a Marseille side on a two-game losing streak will benefit his players.
"It is not necessarily good news that OM remain on a two-game losing streak," said Garde on his club's website.
"OM will do anything to reverse the negative trend.
"We're going to Marseille with great desire and humility. It will require mental toughness, good play individually and collectively."
Garde feels his players will benefit from their Europa league success against Athletic Bilbao.
"This is a good preparation for a game like Sunday," he said.
Garde has doubts over injured duo Yoann Gourcuff and Clement Grenier but Michel Bastos is definitely ruled out.
"I'm not sure that the Marseille game will mark the return of Yoann," said Garde. "He is close to returning. But when he returns I expect from him what I expect from a player who has been absent 10 weeks."
"Regarding Clement Grenier, he is also on the way back. I do not know if he will play on Sunday. As for Michel Bastos, he will not play."
