Edinburgh have five GUINNESS PRO12 wins to their name this season and were on a three-game win streak in all competitions before they met Ulster in their last league game.
A 14-7 defeat to Neil Doak's men preceded the loss in England and du Preez wants to get back to winning ways as soon as possible and is eager to help his side progress in continental competition.
"It is definitely a must-win if we are go to forward and get qualification into Europe," said Du Preez.
"I just think we were not at the races, we were not up for the game as we were against Ulster the previous week.
"We definitely want to put that right this week, it is a massive game, a massive opportunity. It is a big focus this week.
"We had a big talk at half-time [when Edinburgh trailed 26-6], which was pretty gruesome to be honest.
"It just made us realise again how fortunate we are to have this opportunity and we have to make the best of every opportunity we get and should not take anything for granted?this week - we have to put it right."
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