Ben Foden has warned Ulster that Northampton are ready to defy expectations as they seek to reignite their Heineken Cup ambitions.
There will be full live coverage of Saracens v Munster on Sunday Sport on RTÉ Radio 1 on Sunday 16 December from 2pm.
There will be full live coverage of Biarritz v Connacht on a specially extended Sport at Seven on RTÉ Radio 1 on Friday 14 December from 7pm.
Saints dropped to third in Pool Four after being thumped 25-6 at Franklin's Gardens by last season's beaten finalists seven days ago and must prevail in the return fixture at Ravenhill if they are to have any hope of progressing.
Runaway RaboDirect PRO12 leaders Ulster enter tomorrow's showdown on the back of 13 successive wins and are unbeaten at home in Europe since 2008.
The odds are heavily stacked against Saints staying in the hunt for qualification, but England full-back Foden insists they tend to thrive when written off.
"Losing to Ulster stung so much because we were at home and conceded four tries," said Foden.
"We did not play as well as Ulster as a team and obviously we will bridge that gap if we perform to our potential" - Ben Foden
"The performance let us down, as individuals and as a team. There is no finger pointing, we sat down and took the blame as a team, and we know we have to make things better.
"It is a big ask to go to Ravenhill and beat an undefeated side but for us it is about pride and getting back on track.
"A lot of people will write us off, which is probably a good thing, but we are at our most dangerous when teams take us for granted. We will be looking to put in a big performance at Ravenhill.
"We did not play as well as Ulster as a team and obviously we will bridge that gap if we perform to our potential."
Saints are missing captain Dylan Hartley after the England hooker received a two-week ban for striking Ulster front row Rory Best last Friday.
Ulster, who are hoping to reach the quarter-finals for a third successive year, have lost skipper Johann Muller to a fractured arm so Ireland openside Chris Henry leads the team.