A win for the Basque outfit would rescue a frustrating domestic campaign and secure a Heineken Cup spot for the 13th year in a row, as well as handing them a first continental trophy after twice falling at the final hurdle.
And with so much to play for at the home of Amlin Challenge Cup holders Harlequins, Harinordoquyhas told his players they must leave no stone unturned in their quest for the title.
"We may be playing at The Stoop rather than across the road at Twickenham but the venue doesn't matter. What is important is what we can win - whether that's here or somewhere else I don't care," said Harinordoquy.
"After the difficult season we've had with Biarritz we can change everything with one game. It's incredible that we can transform a terrible season into a good one with one match.
"If we win, we can enjoy a great finish and a fresh start for next season. The stakes are huge for this game.
"It's a difficult match to prepare for because there is so much enthusiasm in the squad - maybe that's an enthusiasm we didn't have at the beginning of the season. We now need to use all this enthusiasm to our advantage.
"The goal is to have no regrets at the end of the game. Whatever the result, we must give everything we have as it is our last game of the season."