To do so they must win at Franlin's Gardens this evening and are likely to then have to follow up that up with a favourable result against unbeaten pool leaders Racing 92 in the final round of fixtures.
But Townsend insists his team's meeting with former club Northampton, with whom they lost 26-15 in November, will be tougher than the visit of the French side.
"This is the ultimate test this week, because Northampton are a better scrum than Racing," said Townsend.
"Northampton's lineout drive is the best around, their scrum and their lineout drive.
"We defended their lineout drive last time pretty well but we weren't so good in the scrum.
"We gave away five penalties and one yellow card.
"So that is one area we have been really pleased with - the development of the scrum over the last few weeks."
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