Ligue 1 leaders Rennes could not find a way past inspired Montpellier goalkeeper Geoffrey Jourdren as they slipped to their first defeat of the league season.
Joris Marveaux's header two minutes before the break put the visitors in front, but they were dealt a blow when Garry Bocaly was sent off for a dangerous tackle just after the hour mark.
But despite a host of chances Rennes could not find an equaliser and ended up finishing the game with 10 men as well, Abdou Kader Mangane seeing red in the 83rd minute.
Rennes remained top of the pile despite the defeat, although their lead was cut to one point.
Dimitri Payet missed a stoppage-time penalty against Caen as St Etienne wasted the chance to go top themselves following a 1-1 draw.
Emmanuel Riviere got Les Verts back on level terms eight minutes from time after Youssef El Arabi had put the visitors ahead seven minutes before the break.
Payet was handed the chance to complete the turnaround in the 92nd minute when Jeremy Sorbon fouled Blaise Matuidi, but he blazed his spot-kick over the bar.
Promoted Brest climbed to third in the table - and level on points with St Etienne - with an impressive 2-0 victory at Bordeaux.
Romain Poyet silenced the majority of the crowd when he opened the scoring at the Stade Chaban-Delmas in the sixth minute.
Nolan Roux should have doubled the visitors' lead from the penalty spot midway through the second half but his miss did not prove costly as Benoit Lesoimier made the points safe 10 minutes from time.
An unanswered seventh-minute strike by Julien Feret handed Nancy their first home win of the season against 10-man Lorient and lifted them out of the bottom three in the process.
Nancy have been in dire form at the Marcel-Picot this term, losing four league matches in front of their own fans and going into today's match winless there in six games across all competitions.
Feret ended that with a neat finish from 12 yards, while the visitors saw their hopes of levelling matters dashed by goalkeeper Lionel Cappone's red card after an hour.
Issam Jemaa eased the tension surrounding Lens and the pressure on manager Jean-Guy Wallemme with a last-minute strike to nick a 1-0 win over Nice.
Lens had won only once in Ligue 1 this season heading into the home match, leaving them ahead of only Arles in the table.
They remain next-from-bottom in Ligue 1 but tonight's victory puts them within touching distance of safety.
Valenciennes striker Gregory Pujol piled on the misery for struggling Monaco with two goals in a 2-0 win against the struggling hosts.