The two sides have already met this season with Tandy's men losing out 34-29 in France, despite a comeback that saw them snatch two bonus points at the death.
This time around Tandy insists his side will be looking for the uprights - after turning down a host of kickable penalties - and knows that the clash of his side's mettle.
A victory for Ospreys would mean that they would head into the final Pool 2 fixture with high hopes of reaching the quarter finals.
"It's probably the biggest game we've had at the Liberty for four or five years," said Tandy.
"There is no margin for error and we are playing knock-out rugby two rounds early.
"It's not just going to be a test of our ability. It's also a test of our mental toughness and character. It should be a fantastic occasion.
"We won't be turning down goal-kicking opportunities. If there's three points available, we will be taking those chances.
"That said we will be playing with a positive mindset because we feel we have momentum."
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