Biarritz lost their sixth match of the season on Saturday as they fell 27-21 at home to Grenoble while Jonathan Sexton was super-sub for Racing.
The result leaves BO rooted to the bottom of the standings while Sexton's Racing beat Bordeaux-BÃ¨gles 26-19, with the Irishman scoring a try.
Elsewhere and Toulon moved back to the top of the Top 14 table after edging out Bayonne 18-12 at home while Brive thumped Perpignan 31-6.
Saturday's late game saw Stade FranÃ§ais edge past Oyonnax 16-15 at Stade Charles-Mathon.
Montpellier 43-3 Clermont
Toulouse 26-9 Castres
Biarritz 21-27 Grenoble
Brive 31-6 Perpignan
Racing MÃ©tro 26-19 Bordeaux-BÃ¨gles
Toulon 18-12 Bayonne
Oyonnax 15-16 Stade FranÃ§ais
Biarritz Olympique 21-27 FC Grenoble
Parc des Sports d'Aguilera, Biarritz
If they weren't already, Biarritz are now very much in the midst of a relegation fight in 2013/14 as they fell to their sixth defeat in seven games, this time on home soil against Grenoble.
All of their points came from the boot of scrum-half Dimitri Yachvili, which sums up their lack of attacking threat these days. Grenoble meanwhile scored tries through Matthieu Nicolas, Dayna Edwards and Roland Bernard, which means they pick up the try bonus-point.
Biarritz are now five points adrift of Bayonne, who they face at Stade Jean Dauger next week.
Pens: Yachvili 7
Tries: Nicolas, Edwards, Bernard
Cons: Courrent 2, Hart
Pens: Courrent 2, Bernard
Biarritz: 15 Joe Pietersen, 14 Aled Brew, 13 Benoit Baby, 12 Damien Traille, 11 Teddy Thomas, 10 Daniel Waenga, 9 Dimitri Yachvili, 8 Ueleni Fono, 7 Tanguy Molcard, 6 Benoit Guyot, 5 Pelu Taele, 4 Erik Lund, 3 Francisco Gomez Kodela, 2 Jean Philippe Genevois, 1 Thomas Synaeghel.
Replacements: 16 Romain Ruffenach, 17 Alexandre Menini, 18 Addison Lockley, 19 Joshua Furno, 20 Yann Lesgourgues, 21 Julien Peyrelongue, 22 Seremaia Burotu, 23 Eugene Van Staden.
Grenoble: 15 Fabien Gengenbacher, 14 Benjamin Thiery, 13 Rudolf Coetzee, 12 Julien Caminati, 11 Matthieu Nicolas, 10 Blair Stewart, 9 Valentin Courrent, 8 Florian Faure, 7 Jonathan Best, 6 Cedric Beal, 5 Andrew Farley, 4 Naude Beukes, 3 Dayna Edwards, 2 Anthony Hegarty, 1 Albertus Buckle.
Replacements: 16 Kenan Mutapcic, 17 Vincent Campo Castillo, 18 Hendrik Roodt, 19 Roland Bernard, 20 Jordan Michallet, 21 Ratu Ratini, 22 James Hart, 23 Richard Choirat.
CA Brive-CorrÃ¨ze 31-6 USA Perpignan
Stade AmÃ©dÃ©e-Domenech, Brive-la-Gaillarde
Brive put in an impressive showing to beat Perpignan with a bonus-point for good measure.
Fly-half Riaan Swanepoel crossed twice while former Sale number eight Sisa Koyamaibole scored the home side's third try, with Wales' James Hook kicking two penalties in reply.
Perpignan will undoubtedly rue the three yellow cards they picked up in the game - going to Watisoni Votu, Dewaldt Duvenage and Paulica Ion - as they look to rebuild ahead of hosting Toulouse in the penultimate weekend before the Heineken Cup begins in earnest.
Tries: Swanepoel 2, Koyamaibole
Cons: Germain 2
Pens: Germain 4
Pens: Hook 2
Brive: 15 Gaetan Germain, 14 Guillaume Namy, 13 Arnaud Mignardi, 12 Andrew Mailei, 11 Elia Radikedike, 10 Riaan Swanepoel, 9 Jean Baptiste Pejoine, 8 Sisa Koyamaibole, 7 Dominiko Waqaniburotu, 6 Petrus Hauman, 5 Arnaud Mela, 4 Julien Ledevedec, 3 Patrick Barnard, 2 Guillaume Ribes, 1 Karlen Asieshvili.
Replacements: 16 Francois Da Ros, 17 Johannes Coetzee, 18 Olivier Caisso, 19 Said Hireche, 20 Thomas Sanchou, 21 Thomas Laranjeira, 22 Laurent Ferreres, 23 Kevin Buys.
Perpignan: 15 James Hook, 14 Watisoni Votu, 13 Tommaso Benvenuti, 12 Sione Piukala, 11 Sofiane Guitoune, 10 Camille Lopez, 9 Dewaldt Duvenage, 8 Daniel Leo, 7 Jean Pierre Perez, 6 Justin Purll, 5 Romain Taofifenua, 4 Sebastien Vahaamahina, 3 Giorge Jgenti, 2 Guilhem Guirado, 1 Kisi Pulu.
Replacements: 16 Romain Terrain, 17 Sebastien Taofifenua, 18 Guillaume Vilaceca, 19 Luke Narraway, 20 Nicolas Durand, 21 David Marty, 22 Richard Haughton, 23 Paulica Ion.
Racing MÃ©tro 92 26-19 Union Bordeaux-BÃ¨gles
Stade Yves Du Manoir - Colombes (Paris)
Racing had new signing Jonathan Sexton to thank as his emergence from the bench saw him contribute eight points to the cause against a hugely spirited Bordeaux-BÃ¨gles side.
The hosts were 18-16 ahead before Sexton went over before a late penalty kept Pierre Bernard and Bordeaux, who pick up a losing bonus-point for their efforts, at bay.
Also scoring for Racing was left wing Marc Andreu, whose double set them on their way.
For Racing MÃ©tro:
Tries: Andreu 2, Sexton
Pens: Wisniewski 2, Sexton
Pens: Bernard 4
Racing MÃ©tro: 15 Benjamin Fall, 14 Adrien Plante, 13 Henry Chavancy, 12 Fabrice Estebanez, 11 Marc Andreu, 10 Jonathan Wisniewski, 9 Maxime Machenaud, 8 Camille Gerondeau, 7 Bernard Le Roux, 6 Dan Lydiate, 5 Francois van der Merwe, 4 Karim Ghezal, 3 Brian Mujati, 2 Dimitri Szarzewski, 1 Davit Khinchagishvili.
Replacements: 16 Virgile Lacombe, 17 Luc Ducalcon, 18 Fabrice Metz, 19 Masinivanua Matadigo, 20 Laurent Magnaval, 21 Jonathan Sexton, 22 Benjamin Lapeyre, 23 Soane Tonga'uiha.
Bordeaux-BÃ¨gles: 15 Bruce Reihana, 14 Metuisela Talebulamaijaina, 13 Charles Brousse, 12 Julien Rey, 11 Blair Connor, 10 Pierre Bernard, 9 Emmanuel Saubusse, 8 Taiasina Tuifua, 7 Hugh Chalmers, 6 Louis Madaule, 5 Alikisio Fakate, 4 Jandre Marais, 3 Albert Toetu, 2 Clement Maynadier, 1 Jean Batiste Poux.
Replacements: 16 Benat Auzqui, 17 Jefferson Poirot, 18 Matt Graham, 19 Poutasi Luafutu, 20 Matthew Clarkin, 21 Rafael Carballo, 22 Darly Domvo, 23 Salemane Sa.
Rugby Club Toulonnais 18-12 Aviron Bayonnais
Stade Felix Mayol, Toulon
Many predicted one-way traffic at Stade Felix Mayol on Saturday but Toulon struggled to see off Bayonne, with this 18-12 defeat leaving the visitors languishing in thirteenth position.
Toulon crossed twice in the game, through wings Josua Tuisova and David Smith, but the boot of Bayonne's New Zealander, Stephen Brett, always kept the visitors in touch.
A 63rd minute penalty from Englishman Jonny Wilkinson kept Bayonne six points off the Heineken Cup champions and that was ultimately how things