Blues boss David Young sees no way forward for his team from Pool 1 if they do not avenge last Saturday's 23-15 defeat against the Saints at Franklin's Gardens.
The Welsh outfit are boosted by British and Irish Lions centre Jamie Roberts' appearance on the bench for potentially his first appearance this season after undergoing wrist surgery. And Young knows the Blues must extend their impressive unbeaten Heineken home record of 12 successive wins to stay in touch with group leaders Northampton.
"We have to win," said the former Wales prop. "If we don't, we are out of the competition, but also we have to make sure that Northampton leave with nothing."
Leicester, having collected a losing bonus point away to Perpignan last weekend, will remain on course for the quarter-finals from Pool 5 if they beat the Catalans at Welford Road today.
Italian prop Martin Castrogiovanni returns to bolster a Tigers pack that endured a difficult afternoon at the Stade Aime Giral, with England tighthead Dan Cole named among the substitutes.
Wasps, tucked in two points behind Pool 6 leaders Toulouse, cannot afford any slip-ups against Adams Park visitors Newport Gwent Dragons. Although Wasps scored three tries to topple the Dragons in Wales six days ago, it was an unconvincing display, but rugby director Tony Hanks has named an unchanged side. England centre Riki Flutey, meanwhile, features on the bench following his recovery from a calf muscle injury that has sidelined him since late October.
The Dragons, without a European win this season, have Wales lock Luke Charteris back from injury, but a knee problem sidelines fly-half Jason Tovey, so Matthew Jones deputises.