Lyon, who host mid-table Toulouse on Sunday, have slipped from second to fourth in the standings after losing three league games in succession for the first time since 1993.
They trail second-placed Marseille, who occupy the last direct Champions League qualifying spot, by four points with seven games left.
Third-placed St Etienne are ahead of Lyon on goal difference with 53 points and can open a provisional three-point lead over their rivals when they visit mid-table Valenciennes on Friday.
"Something is being broken and I am quite worried," Lyon coach Remi Garde said after OL suffered a humiliating 2-0 defeat at lowly Stade Reims last weekend.
"I see there is less enthusiasm in the team and when an effort is being made it is more individual than collective."
Lyon, French football's shining light in the last decade when they won seven league titles in a row from 2001, played in the Champions League for 12 straight years but were in the Europa League this term after finishing fourth in Ligue 1 last season.
To stay in touch with St Etienne and hold off fifth-placed Lille, whose remarkable rise has taken them within a point of Lyon, Garde's struggling team will need Bafetimbi Gomis and Lisandro Lopez to rediscover their scoring touch.
Gomis has netted only twice this year while Lisandro has scored three times since January with OL losing all three games.
St Etienne, on the other hand, have been able to rely on their trusty Gabon striker Pierre-Emerick Aubameyang, seven of whose 17 league goals this season have come in 2013 helping Les Verts to establish a 16-game unbeaten run.
Lille, who won seven of their last eight league games, are on a high as they entertain Marseille on Sunday looking to benefit from any slip up by St Etienne or Lyon.
"We will have no pressure because we are coming back from so far behind," Lille midfielder Florent Balmont told the club website.
OM, though, have shown they have the ability to win ugly, having ground out 10 1-0 league victories this season.
Nice, sixth on 51 points, are one point behind Lille and also eyeing third place as they prepare to host strugglers Sochaux on Sunday.
- Sports & Recreation
- St Etienne