Ireland wing Tommy Bowe has warned his Ulster team-mates that Saints will come at them ‘twice as hard’ this week.
Bowe got on the scoresheet as the last season’s Heineken Cup runners-up clinched a bonus-point 25-6 win at Franklin’s Gardens on Friday night.
Saints struggled in the majority of departments as they were eclipsed by the RaboDirect PRO12 table-toppers.
And Jim Mallinder’s men now have a real fight on their hands as they aim to make amends in Belfast on Saturday night.
Bowe will hope to put them to the sword once more as Ulster look to move one step closer to qualifying for the knockout stages, but he knows it won’t be a straightforward task.
“We know that Northampton are going to come to us this week and come at us twice as hard,” said Bowe, whose appearance against Saints was his 50th in European competition.
“Yes we took a bonus point out of Franklin Gardens, but they (Northampton) made us work hard for that win.
“It was not until the final minute or two that we went in for the fourth try to secure that bonus.”
Ulster now sit six points clear at the top of pool four, having accrued 14 from their three games so far.
Castres are second on eight, with Saints amassing six, and Bowe has warned his side not to get complacent.
He said: “We can be massively pleased to have made it four wins on the bounce away from from home, but in terms of Europe, the job is only half done.
“We have to do it all again this week, and we will have to be up another per cent on our game again.”