Montauban were relegated from the French Top 14 on Saturday after Montpellier's Argentina centre Justo Piccardo scored four tries in a 59-7 hammering.
Piccardo's contributions sent Montauban and their meagre financial budget down to ProD2 after just one season, when they managed just one win and a draw by conceding a record number of a tries in one Top 14 campaign.
Montpellier crossed for nine touchdowns in total as they moved to second place, seven points off leaders Toulouse, who head to Toulon later in the day.
They leapfrogged Pau, who had beaten Castres 27-15 earlier in the day thanks to 11 points from English fly-half Joe Simmonds.
Montauban, coached by former France scrum-half Sebastien Tillous-Borde had to beat Montpellier to keep any hope of overlapping Perpignan in 13rd place, the relegation play-off berth.
That aspiration was all but over by halftime on the Mediterranean coast as Montpellier led 26-0, thanks to Piccardo crossing three times in 33 minutes.
The only consolation for 1967 French champions Montauban was a try for 19-year-old Fijian winger Asaeli Gade as Montpellier added five tries after the break, including 24-year-old Piccardo's fourth.
Elsewhere, fellow strugglers Perpignan will face the loser of the ProD2 promotion final in a relegation play-off after also suffering a heavy defeat, losing 45-14 at Clermont.
Former New Zealand fly-half Harry Plummer scored 20 pointsfor Les Jaunards, who stregthened their grip on a play-off spot.
Scrum-half Maxime Lucu slotted a 76th minute conversion as Bordeaux-Begles edged Bayonne 40-38 a week on from reaching the Champions Cup final.
Lucu's side are in the sixth and final play-off spot, four points below Stade Francais in fourth after the Parisians thumped Lyon 59-17.
On Sunday, Racing 92 host Ronan O'Gara's La Rochelle with both sides still holding a mathematical chance of reaching the top six.