Chris Boyd believes Saints will be squaring up to 'the most impressive side in Europe' at Stade Marcel Michelin tonight (kick-off 8pm GMT).
The black, green and gold are in France to face Clermont Auvergne, who won 41-20 at Franklin's Gardens on October 13.
Clermont are currently top of the French Top 14, having won 10 of their 14 league games so far this season.
And they are also leading the way in Saints' Challenge Cup pool, having claimed a bonus-point win from each of their four matches so far.
Clermont are the only side in European competition to still possess a flawless record during the current campaign.
And Boyd knows this weekend's Challenge Cup encounter will be as tough as they come.
"They're probably currently the most impressive side in Europe, certainly justifiably top of the French league," the Saints boss said.
"They're an absolute handful and they were one side this year that we have no qualms that they were too good for us here when we played them towards the start of the season.
"We're going to have to find and way to be on top of our game and have an impact on their game to stay in the hunt.
"They're very strong all over the place. They're a huge team, very physical, very fast, play with a lot of freedom, have some outstanding players in their team.
"They're genuinely currently a great side.
"We're just going to have to try to do what we do best, impose our will on them and hope we can have an impact."
Saints were steamrollered at scrum time when they hosted Clermont earlier in the season.
And it has not been an area of strength for Boyd's side in the Gallagher Premiership.
But the boss believes things are getting better.
"From an outcome point of view, the scrum has been patchy but that's reflective of our whole performance really," Boyd said.
"We had a good period for three or four weeks where we were going in the right direction and then Exeter was a bit of a handful for us.
"Overall, the trend is going north.
"We're working hard and we've currently got a squad where we trade off the physical size in the scrum with the work rate around the field.
"Our props do an enormous amount of work and our hybrid locks do contribute a lot to the game around the field.
"We're not a power scrummaging team and we've just got to find a way to live with those that are."