Toulon welcomed back coach Pierre Mignoni on Saturday but crashed to a 46-27 home defeat to Stade Francais.
Mignoni was on the touchline for the first time since suffering what he called a 'breakdown' in February.
Toulon led 20-16 a minute before half time after the visitors incurred two first-half yellow cards, but a try by Juan Martin Scelzo just before the break put Stade ahead for good, despite a third yellow card midway through the second half.
While the visitors were ill-disciplined, the home team were sloppy, racking up turnovers and mistakes as they suffered a second straight heavy home loss.
Italian hooker Gianmarco Lucchesi scored two tries for Toulon and Esteban Abadie touched down in the closing minutes.
The Parisians scored six tries with Leo Barre grabbing two.
"We gave them a lot of easy points and didn't score ourselves," said Mignoni. "In my view, they shouldn't have been in the game in the first half, and that carried over into the second half."
Mignoni took a break on medical advice after a home loss to Clermont on Valentine's Day.
"I don't feel the same way I did after the game against Clermont," he said. "I feel bad for the players, but it's not over yet. We're going to stick together and see what happens."
Stade climbed to fourth in the standings. Toulon continued their slide and are eighth, five points outside the playoff places.
Earlier, Montpellier clawed their way up to second in the standings when Tom Banks scored their only try with two minutes left to grab a 20-17 victory at Clermont after playing the last 19 minutes with 14 men.
Pita-Gus Sowakula and Anthime Hemery scored tries for the hosts. Harry Plummer converted both and booted a penalty. But Domingo Miotti kicked four penalties and Leo Coly one to keep Montpellier in touch after Lennox Anyanwu was shown a red card in the 61st minute for flattening Plummer.
"I'm very proud of my players, who never gave up or let up," said Montpellier coach Joan Caudullo. "After the red card, we could have let up, but we never did."
Clermont dropped to fourth in the table.
Racing 92 conceded two tries in the first seven minutes but roared back to beat Castres 52-21 and are outside the playoff places only on points differential.
Lyon fought back from 12 points down to win 32-28 at second-bottom Perpignan.
"It could have gone either way at the end of the match," said Lyon manager Karim Ghezal. "We didn't give up, we didn't panic."
Bayonne ran in nine tries as they thrashed last-placed Montauban 60-26.
Pau can reclaim second spot when they visit struggling La Rochelle in the Saturday evening game. On Sunday, runaway leaders visit European champions Bordeaux-Begles, who occupy the sixth and last playoff spot.