Olly Barkley accepts that Bath have reached the make-or-break stage in their Heineken Cup campaign.
The 1998 European champions head to Belfast on Saturday for a Pool Four appointment with Ulster before Saturday week's Recreation Ground return fixture.
Bath back Barkley knows the west country club cannot afford any further mishaps after losing at home to group leaders Biarritz in October, and said: "These next two games will decide whether us or Ulster will challenge Biarritz to go through, so this game is like a semi-final for us."
Current Aviva Premiership leaders Northampton can tighten their grip on Pool One on Saturday by seeing off Franklin's Gardens visitors Cardiff Blues.
The Saints, beaten once in domestic league and European action this term, were taken to the wire by previous Heineken Cup opponents Castres and Edinburgh, but still emerged victorious.
"The back-to-back games in this competition are always very important," said Northampton rugby director Jim Mallinder. "Cardiff Blues won the Amlin Challenge Cup last season by beating Toulon in Marseille, so we know how good they are. I think the match will be a cracker."
Saints' midlands rivals Leicester - the only side with a maximum 10 points from two games in this season's Heineken Cup - will put their unbeaten record on the line against Pool Five hosts Perpignan on Saturday.
Saracens also face French opposition on the resumption of Heineken Cup action, tackling Racing Metro at Vicarage Road following successive defeats against Clermont Auvergne and Leinster.
Elsewhere, reigning European champions and Pool Six favourites Toulouse visit Glasgow on Friday, while on Saturday Edinburgh visit Castres, the Scarlets host Treviso in Pool Five and Biarritz visit Italian minnows Aironi.
Sunday's action sees Jonny Wilkinson and Toulon facing London Irish at the Madejski Stadium, with Munster - likely to be boosted by lock Paul O'Connell returning from injury - entertaining the Ospreys, Newport Gwent Dragons meeting Wasps and Leinster visiting Clermont.