A first-half try from Iain Balshaw helped Biarritz to a 17-0 Heineken victory over Connacht in horrendous conditions at Parc des Sports Aguiléra on Friday.
Connacht were unable to repeat their heroics of a week ago as Biarritz took revenge for last week's loss in Ireland in Pool Three.
The saturated pitch contained pools of water in certain areas but the ground staff cleared enough of it for the fixture to go ahead as scheduled in heavy rain.
Balshaw's try and five points from the boot of Dimitri Yachvili sent the French side into half-time with a comfortable 10-0 lead.
Although there were two yellow cards to the hosts' Benoit August and Thibault Dubarry, a late touchdown from Seremaia Burotu secured the home team's second victory in Europe this season.
The Top 14 outfit were left reeling earlier in the week when president Serge Blanco sacked coaches Jack Isaac and Serge Mihas following their 22-14 defeat to the Pro12 team.
However, it didn't prevent the hosts from imposing themselves on the Irish province here as they dominated the early exchanges.
Yachvili slotted a penalty and decent handling in atrocious conditions sent Takudzwa Ngwenya away, but despite having crossed the whitewash, the American international was adjudged not to have touched down.
3-0 it stayed until the 31st minute when the Biarritz backs defied the rain-sodden evening to score a well-worked try off the back of a scrum.
It was eventually finished off by former England international Balshaw, with their scrum-half converting, to extend the advantage to 10-0 at the break.
The French side continued to have the majority of the chances at the start of the second half, but August's sin-binning allowed Dan Parks an opportunity to reduce the deficit.
However, his kick was well wide. And although Dubarry became the second player for the Top 14 team to be yellow carded, Connacht couldn't force a breakthrough. Biarritz were meandering to victory and put the finishing touches to a good night when Damien Traille latched onto his own kick, taking advantage of a fortuitous bounce to put replacement centre Seremaia Burotu over in the final minute.
Tries: Balshaw, Burotu
Cons: Yachvili 2
Yellow cards: August; Dubarry
Biarritz: 15 Iain Balshaw, 14 Taku Ngwenya, 13 Jean-Pascal Barraque, 12 Damien Traille, 11 Aled Brew, 10 Julien Peyrelongue, 9 Dimitri Yachvili, 8 Imanol Harinordoquy (c), 7 Raphael Lakafia, 6 Wenceslas Lauret, 5 Pelu Taele, 4 Erik Lund, 3 Francisco Gomez Kodela, 2 Benoit August, 1 Fabien Barcella.
Replacements: 16 Jean-Philippe Genevois, 17 Lodewicus Blaauw, 18 Thomas Synaeghe, 19 Thibault Dubarry, 20 Magnus Lundy, 21 Yann Lesgourgues, 22 Seremaïa Burotu, 23 Marcelo Bosch.
Connacht: 15 Robbie Henshaw, 14 Tiernan O'Halloran, 13 Danie Poolman, 12 Dave McSharry, 11 Fetu'u Vainikolo, 10 Dan Parks, 9 Kieran Marmion, 8 Eoin McKeon, 7 Johnny O'Connor, 6 Andrew Browne, 5 Mike McCarthy, 4 Mick Kearney, 3 Ronan Loughney, 2 Jason Harris Wright, 1 Brett Wilkinson.
Replacements: 16 Ethienne Reynecke, 17 Dennis Buckley, 18 JP Cooney, 19 Danny Qualter, 20 George Naoupu, 21 Paul O'Donohoe, 22 Miah Nikora, 23 Matthew Jarvis.
Venue: Parc des Sports Aguiléra
Referee: Leighton Hodges (Wales)
Assistant Referees: Sean Brickell (Wales), Chris Williams (Wales)
Television Match Official: Gareth Simmonds (Wales)