West country rivals Bath and Gloucester will battle it out on Saturday for the top quarter-final seeding in this season's Amlin Challenge Cup.
Both clubs have already qualified for the last eight, but Bath occupy pole position.
Victory over Recreation Ground visitors Bucharest would secure the number one berth and a probable home quarter-final against 2001 Heineken Cup finalists Stade Francais.
Any slip-up, though, and Gloucester would overtake Bath by defeating Kingsholm visitors Mont-de-Marsan.
Wasps and Perpignan are also through as pool winners, while Stade Francais need a point against already-eliminated London Welsh in Paris to confirm they progress.
The five Amlin group winners will be joined by three runners-up from Heineken Cup pools for the quarter-finals in early April.
Bath University student Tom Dunn makes his debut against Bucharest, packing down at hooker alongside front-row colleagues Charlie Beech and Anthony Perenise, with lock Stuart Hooper returning to captain Bath.
Despite snow in the west country today, the Recreation Ground pitch has been covered with a heated tent since last weekend, and the game is not in doubt at this stage.
Gloucester are also confident their Kingsholm pitch will beat the elements, and rugby director Nigel Davies has named a strong side that includes England internationals Freddie Burns and Charlie Sharples, with Scotland lock Jim Hamilton as skipper.
"If you look at the groups and how they've panned out, there is no doubt in my mind that we've got the toughest group with two Top 14 teams and another Aviva Premiership side in London Irish," Davies said.
"So, for us to be five (wins) from five at this stage, we can be very pleased with that.
"But it's important that we finish on a high note with a big performance and a win which allows us a home quarter-final, which would be a fantastic occasion."
Gloucester were beaten 18-12 by Irish in the Premiership a fortnight ago, and Davies added: "We've got to be guarded against complacency.
"I would like to think we've learnt our lesson on that from the London Irish game. I hope, and I sincerely believe, that the Gloucester crowd will see a different team this weekend."
Wasps have seemingly done enough for home advantage in the first knockout phase, but rugby director David Young was left distinctly unimpressed by their 20-19 victory over Newport Gwent Dragons last night that took them to 25 points.
"We were totally unrecognisable from the team we have been over the last six weeks. We were awful," Young said.
"There are a lot of excuses I could make, but if I am straightforward about it there wasn't an area that I was happy with."
Perpignan's bonus point success against Rovigo last night knocked Worcester our of the tournament.
Although the Warriors will finish level with Perpignan if they claim a bonus point success against Sixways visitors Gernika on Saturday, try countback over their two appointments with the French club counts against them.
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