Stade Français were the big winners in the Top 14 on Saturday after running six tries past Castres to claim all five points in Paris.
At the other end of the table, Bayonne were the big losers as the Basques dropped into the relegation zone after defeat at home to Bordeaux-Bègles.
Brive are not much better off having been outclassed at home by Montpellier.
By contrast Toulouse increased their advantage at the summit of the standings thanks to a six-try demolition of Lyon, who are now stone last following Biarritz's victory on the road to Agen on Friday.
Perpignan meanwhile were forced to settle for a drew at home to Racing-Métro.
There was however bad news for new France coach Philippe Saint-André after Toulouse lock Romain Millo-Chluski sustained a serious shoulder injury.
Agen 6-15 Biarritz
Bayonne 20-27 Bordeaux-Bègles
Brive 9-23 Montpellier
Stade Français 38-21 Castres
Toulouse 51-10 Lyon
Perpignan 14-14 Racing-Métro.
Sunday, January 8
Clermont v Toulon
Stade Français Paris 38-21 Castres Olympique
Stade Charléty, Paris
Stade Français climb to fifth in the standings as they bounce back from last week's disaster with a very important win in a nine-try crowd pleaser.
Castres were left shell-shocked by a 20-minute opening blitz from the hosts that saw the Parisians score four tries to lead 28-0!
Sergio Parisse and Pascal Papé had touched down within eight minutes of kick-off, and were soon joined on the scoreboard by Julien Arias and Paul Sackey as Castres were made to pay for a series of clumsy errors.
Castres were given a glimmer of hope when Dimitri Szarzewski saw yellow and Seremaia Baï scored to open the visitors' account and leave the scores at 28-7 at half time.
The Arias try was the pick of them.
It started from a counter-attack from deep within their own 22 with Argentinian star Felipe Contepomi playing a leading role before Arias went for the line, just getting the nod from the video referee after he had been tap-tackled by Max Evans.
Castres launched a counter-attack desperately trying to reduce the deficit before the break - their captain and former All Black Chris Masoe just coming up short before the line.
However, Stade had France hooker Dimitri Swarzweski sin-binned nine minutes from half-time after persistent infringements by him and his team-mates and Castres did not let that advantage slip.
Veteran Fijian centre Seremaia Bai burst through the Stade defence to touch down under the posts for his second try of the campaign - Pierre Bernard converted to give them some hope.
That was dashed within a minute of the restart as a great break by Contepomi tore apart the Castres defence and a sweet flicked pass to Pierre Rabadan saw the experienced flanker run in their fifth try. Dupuy failed for the first time with the conversion.
Castres stuck to their task scoring a second try in the 50th minute as the outstanding Masoe found lanky winger Romain Martial and he made no mistake - Romain Teulet adding the extras.
However, Stade shrugged that off and almost at will scored another try -a second one for Arias which Dupuy converted.
Thierry Lacrampe scored a late consolation try for Castres but it wasn't enough to deny Stade a bonus point for winning by three tries.
Stade Français: Warwick - Sackey, P.Williams, M.Rodriguez, Arias - F.Contepomi, J.Dupuy - Rabadan, Parisse (cap), Lyons - Papé, Mostert - Attoub, Szarzewski, S.Wright
Replacements: Sempéré, Slimani, Palmer, LaValla, Fillol, Turinui, Plisson, De Malmanche
Castres: Teulet ; Martial, Sanchou, Baï, Evans ; Bernard, Kockott ; Malonga, Masoe, Diarra ; Murray, Rolland ; Wihongi, Bonello, Peikrishvili.
Replacements: Rallier, Taumoepeau, Bornman, Caballero, Lacrampe, Lakafia, Bonnefond, Ducalcon.
Stade Toulousain 51-10 Lyon Olympique
Stade Ernest Wallon, Toulouse
No surprises in Toulouse then as the defending champions cemented their spot at the top of the table for another month (at least).
With a fortnight of crucial European clashes ahead, Guy Novès's team assured everyone that the Big Red Machine is firing on all cylinders by attacking from anywhere and everywhere.
The bad news is that newly-recruited hooker Akvsenti Giorgadze lasted just 15 minutes before leaving the field injured. 'Medical joker' indeed! Lock Romain Millo-Chluski's late injury could also be a season-ender.
The hosts led 23-10 at the break thanks to tries from Maxime Médard, Yannick Nyanga and a handful of penalties from Lionel Beauxis.
Lyon's only try came from wing Franck Romanet, after some good work from Ricky Januarie.
Shaun Sowerby extended the hosts' lead after the break before a late flourish saw Yves Donguy and Florian Fritz score and Médard bag his second try.
Toulouse: Poitrenaud - Matanavou, David, Jauzion, Médard - Beauxis, Doussain - Nicolas, Sowerby, Nyanga (cap) - Albacete, Lamboley - Johnston, Giorgadze, Poux
Replacements: Montès, Steenkamp, Millo-Chluski, Picamoles, Burgess, Fritz, Donguy, Boutemane
Lyon: Van Gisbergen - Romanet, Thomas, Fatafehi, Grosso - Sadourny (cap), Januarie - Leguizamon, Koyamaibole, Bontinck - Basson, Sousa - Toleafoa, Bonrepaux, Fiard
Replacements: Colliat, Tchougong, Marchois, N'Zi, De Bruyn, Lespinas, Tranier, Roux
Aviron Bayonnais 20-27 Union Bordeaux-Bègles
Stade Jean Dauger, Bayonne
This is catastrophic result for Bayonne, who drop into the relegation zone, behind Biarritz by virtue of their loss to their Basque rivals earlier this season. It's Bayonne's fourth loss in five games.
Bordeaux arrived looking more a morale-boosting performance after forwards coach Laurent Armand was hospitalised following a stroke mid-week and is still in a coma.
And it was les Girondins who took the early advantage when Samoan hooker Ole Avei crashed over in the third minute following a bad pass from Bayonne wing Joe Rokocoko inside his own 22.
Wing Thierry Brana touched down for UBB's second try just before the break to give the visitors a 20-6 lead and Avei scored his second soon after the restart to put Bordeaux firmly in front.
Sam Gerber's try got Bayonne back on track but soon afterward his fight with Daniel Leo saw the letter sent to the sin bin. A few minutes later a general dust-up broke out with Dwayne Haare and Silviu Florea both seeing yellow.
Bayonne prop Aretz Iguiniz's try on the hour mark secured a losing bonus point for the hosts, but it will come as scant consolation.
Bayonne: Heymans - Rokoçoko, Lacroix, Mazars, Gerber - Boyet, M.Phillips - Marmouyet, Lauaki, Haare - Boutaty, Linde - Tialata, Roumieu, Iguiniz
Replacements: Da Ros, Manukula, Flavell, Baget, C.Garcia, Otazo, O'Connor, Avril
CA Brive Corrèze 9-23 Montpellier HR
Stade Amédée Domenech, Brive
Montpellier stayed firmly in the hunt for a top six place with a comfortable win over Brive, who can contemplate a hard relegation battle as their winless run stretches back to October 22.
Despite an indisciplined display that saw them receive three yellow cards ( prop Giorgi Jgenti and number eight Alex Tulou got their marching orders in the ninth and tenth minute respectively) Montpellier controlled the game from start to finish.
A try from wing Yoan Audrin just before the break gave the visitors a 13-6 lead and Tulou made up for his indiscretions with a try on the hour mark to secure victory.
Montpellier: Amorosino - Bustos Moyano, Combezou, P.Bosch, Audrin - Trinh-Duc, J.Tomas - Gorgodze, Tulou, Ouedraogo - Privat, Hancke - Jgenti, Van Vuuren, Leleimalefaga
Replacements: Creevy, Nariashvili, De Marco, Martin, Paillaugue, Matadigo, S.Fernandez, Bustos
USA Perpignan 14-14 Racing-Métro 92
Stade Aimé Giral, Perpignan
A frustrating result for Perpignan who are left in tenth position, just four points clear of the relegation zone while Racing climb back into the play-off places in sixth.
USAP might not have got the four points but for once some plenty of plosive intentions and attacking play and will harbour numerous regrets having had the better of both territory and possession.
Indeed it took the hosts just 47 seconds to score their first and only try after James Hook broke clear in midfield to set up wing Farid Sid.
Parisian fly-half Jonathan Wisniewski landed two penalties to leave the scores at 8-6 to the locals at half time.
Hook and Wisniewski traded penalties before Racing wing Juan José Imhoff scored a brilliant individual try from his own half on the hour mark to give les Franciliens a 14-11 lead.
But Hook was on target with his third penalty in the 70th minute to level matters.
Perpignan: Michel - Sid, Mermoz, Marty, R.Coetzee - Hook, Boulogne - Tonita, Chouly, Guiry - Tchale Watchou, Olibeau - Mas (cap), Guirado, Schuster
Replacements: Géli, Pulu, R.Taofifenua, Le Corvec, J.-P.Pérez, Cazenave, Hume, Bourrust
Racing-Métro: Imhoff - Bobo, Chavancy, Estebanez, Saubade - Wisniewski, Lorée - Battut, Cronje, Vaquin - Van der Merwe, Nallet (cap) - Tuugahala, Noirot, Brugnaut
Replacements: Arganese, Lo Cicero, Ghezal, Leo'o, Descons, Matavesi, F.Steyn, Orlandi