NORTHAMPTON head coach Jim Mallinder has billed tomorrow night's Heineken Cup clash against in-form Ulster as "a massive challenge" for his players.
Ulster will arrive at Franklin's Gardens as the only remaining unbeaten team in European rugby's leading three domestic leagues this season - the Aviva Premiership, the RaboDirect PRO12 and the French Top 14.
They have won all 10 of their league games, while they also enjoy a three-point advantage over Saints in Heineken Cup Pool Four, which ramps up the pressure on Northampton tomorrow and for next week's return fixture.
"Ulster have a strong winning habit this season and are coming to Franklin's Gardens in the best possible form," Mallinder said.
"Their squad is full of talented players who time and again this season have shown a never-say-die attitude and the ability to get the scores when they needed them.
"It is going to be a massive challenge for us, we know that. But training has been very positive this week and we are coming into the game on the back of three successive wins ourselves.
"However, all of the players know that they will have to take a step up from those performances and play for the full 80 minutes if we are to get the result we want."
England flanker Tom Wood returns from autumn Test duty to pack down at openside for Saints, while full-back Ben Foden also features after making a successful return from injury against Premiership opponents Sale last Friday.
Ulster, last season's Heineken Cup runners-up, will arrive in the midlands with a powerful line-up that features the likes of Tommy Bowe, Ruan Pienaar, Rory Best and former Northampton number eight Roger Wilson.
"They (Northampton) have a strong pack and they build their game around that," Ulster coach Mark Anscombe said.
"Their set-piece is very strong and we've got to be excited about meeting that. We've got to conquer them up front if we are going to compete because you've got to have front-foot ball.
"The tight-five have to step up and show their qualities, but I am confident in them. They have all played international rugby."
Glasgow's hopes of having an impact on Pool Four will disappear if they fail to beat visitors Castres tomorrow night. After successive losses against Northampton and Ulster, Gregor Townsend's team currently prop up the group.
"We are coming off the back of what was a disappointing performance against Munster last week, particularly as we believed we were capable of leaving Thomond Park with a win," Townsend said.
"We pride ourselves on being tough to beat, and we didn't do that in Ireland. There has been a renewed determination this week, as that was a difficult defeat to take.
"We know our record in the Heineken Cup is not as good as it should be, and we are fighting to stay in the tournament.
"The next two games (Castres home and away) will determine how the rest of our season will go. We will be doing all we can to still be in contention in this competition."
And in the Amlin Challenge Cup tomorrow, London Welsh visit Grenoble after keeping alive their quarter-final hopes with a 32-31 victory over Cavalieri Prato during the competition's last round of action in October.
Coach Lyn Jones has made 14 changes from the side that accounted for Premiership rivals London Irish last weekend, with only full-back Tom Arscott remaining.