Ospreys coach Steve Tandy knows his side have reached crunch time in the European Champions Cup as they head into their penultimate Pool Five clash with Northampton on Sunday.
Victory for Saints sets up a winner-takes-all clash against Racing Metro in Northampton next Saturday but Ospreys do have an outside chance of progressing, but it's not guaranteed even if they beat both Northampton and Treviso next weekend. Racing and Treviso meet in Paris on Sunday.
"When you have the Aviva Premiership champions and current leaders coming to town, then you know it's going to be a big occasion," Tandy said. "It's do-or-die for us this weekend as far as Europe is concerned, so we know that we've got to go out there and give it everything.
"If we can get the performance right, then who knows what can happen? All we can do is look after the areas that we can control, and hopefully take it down to the final weekend for us out in Treviso. One thing we have seen with this group is that they will never give up on anything. It's going to be a great contest between two good teams - something to get excited about."
Saints welcome back skipper Dylan Hartley after a three-week suspension for elbowing but are without the hooker's England colleague Courtney Lawes, so Sam Dickinson continues at lock.
"We are top of the pool and are in control of our destiny. We know that two wins will see us qualify," Saints rugby director Jim Mallinder said.
In Pool Four, high-flying Bath face Toulouse requiring victory to keep alive their hopes of progression. Sam Burgess has a knock, while injury also sidelines wing Semesa Rokodugun and Paul James captains the side.
Bath lost 21-19 when the teams met in the west country three months ago, and Bath head coach Mike Ford expects a different type of challenge this time around.
"They (Toulouse) have changed the way they play since last time," Ford said. "They had gone through a few defeats when they played us at home. They were very cautious and quite easy to read. They are running the ball from their in-goal area now, turning penalties down at goal which are kickable, taking quick lineouts, quick taps and quick 22 restarts.
But they have got a lot to lose at the weekend. They are at home and they're the favourites to go through. We are excited about playing Toulouse at their place - we want to see how good we are."
Also in Pool Four, Glasgow face already-eliminated Montpellier, with a winning keeping them in the race for the knockout stages.