Northampton centre James Wilson has warned his team-mates that Castres will be eager to uphold their proud home record.
The Saints line up against the Top 14 champions at Stade-Pierre Antoine on Saturday in the opening round of the Heineken Cup, and Wilson expects a fiery start from their hosts.
Though Castres lie 11th in their domestic league standings, they are yet to lose a home fixture.
"The Heineken Cup's going to be pretty massive," Wilson told the Northampton Chronicle.
"Away from home in France, it's going to be tough.
"Obviously I had a season over there and I know the French lads get up for the ones at home. They focus on winning all of them so they'll put out a very strong team.
"They'll give it a good crack and defend their home turf. We know going into it that they're a strong side and will be really competitive at the weekend."
Saints are under no illusions regarding the size of their task on Saturday, but Wilson feels a strong start to the tournament is vital in what has been termed the "pool of death", with Leinster and the Ospreys the other two sides in the group.
"It's crucial to win on Saturday, especially with the sort of group we're in," he added.
"Every point counts so we'll be going in there to take them out. But we know it's going to be a tough one first off.
"Castres away last season, we lost that one and it put us on the back foot for the rest of the competition so we want to get a win.
"That's what we're focused on getting so we'll go away and give it our best shot."