Marseille join Lyon -- 2-1 winners at Rennes on Friday -- provisionally top of Ligue 1 to give Rudi Garcia's side a timely boost ahead of next week's Europa League first playoff round game at Slovenia's Domzale.
Saint-Etienne also have maximum points under new Spanish coach Oscar Garcia, sitting third on goal difference after Romain Hamouma's second half goal sealed a 1-0 win at Caen.
But former Leicester City boss Ranieri's Nantes side followed last week's 3-0 loss to Lille with another defeat after an unprecedented injury spate in the first half hour.
Right back Leo Dubois had already been declared unfit just before the game forcing Ranieri to reorganise his starting eleven.
And the Italian was despairing as midfielder Valentin Rongier suffered a shoulder injury early and was forced off followed by striker Yacine Bammou and midfielder Alexander Kacaniklic -- both with muscle problems.
"It's the first time in my career that I've had to change three players in 25 minutes," declared a frustrated Ranieri.
"Luck isn't on our side right now. But their replacements were good and the second half was very good."
Nantes held on largely thanks to goalkeeper Ciprian Tatarusanu, who arrived this summer from Fiorentina, and pulled off six saves in the first half.
There was relief when Florian Thauvin's late goal was refused as offside but the Romanian keeper was unable to prevent Argentine Ocampos at the far post from getting through on 86 minutes.
The Canaries missed two golden chances to snatch a point with two quick-fire Emiliano Sala headers hitting the post.
Toulouse, meanwhile, got back to winning ways for the first time since April 2 with Swedish international Jimmy Durmaz's converted penalty sealing a 1-0 win at home against Montpellier.
Elsewhere Angers won 2-0 at Amiens with Bordeaux beating Metz by the same scoreline at home.
On Friday, Nice suffered their second setback falling 2-1 at home to promoted Troyes to dampen confidence ahead of next week's Champions League play-off at Napoli.
The Riviera outfit, third last season, were without their two star players, the injured Mario Balotelli and new Dutch signing Wesley Sneijder, who watched from the stands.
Lyon followed on last weekend's 4-0 thumping of Strasbourg with a 2-1 win at Rennes.
Meanwhile, all eyes will be on Neymar's much-hyped Paris Saint-Germain debut on Sunday at Brittany side Guingamp after his world record move from Barcelona.