For the trip to Franklin's Gardens, the Ospreys name a forward pack that would be the envy of most sides. There are five British & Irish Lions in the front eight and that is without Ian Evans who misses the tie with injury.
"This is a big game for us, one that everybody in the camp is really looking forward to," said Tandy.
"We didn't do ourselves justice at the Liberty on Saturday, we had the third biggest Heineken Cup crowd of the weekend and it's disappointing we weren't able to reward such a big turnout with a good performance.
"We are well aware we need to make some big improvements if we are going to put in the kind of performance at Northampton that we need. They are in the same boat as us having also lost their first game, so no doubt there'll be a tension and edge to the game."
After struggling at times to break down Leinster last weekend, Tandy keeps most of the same backline against Northampton though Tom Habberfield comes in for Tito Tebaldi at scrum half. Jeff Hassler makes his first Heineken Cup start. The Saints include Wales wing George North but former Ospreys man Kahn Fotuali'i has to settle for a place on the bench.
"This is a very difficult group but there's still everything to play for and there's going to be plenty of twists and turns," said Tandy.
"We can't worry about what the other teams in the group do, we've got to fight all the way and make sure we put ourselves in a position to take advantage of the twists and turns. We have to show what we are about on Sunday.
"It's going to be a big test of character and attitude and we'll have to front up to a big, physical team, but that's an exciting prospect."