The Irish region, reigning European champions, are preparing to face Clermont for the fourth time in three seasons and for the first time since their 19-15 victory in the 2011/12 semi-final.
And they go in off the back of a much-needed bonus-point 37-7 victory over Zebre in the RaboDirect PRO 12, whilst also boasting a 17-game unbeaten European streak.
But after the French side extended their own unbeaten run at Stade Marcel Michelin to 50 games with victory over Top 14 leaders Toulon before the international break, Nacewa admits their task is an ominous one.
"It has just turned into a bit of a derby battle over the last few years," said Nacewa. "I have always said they are one team you don't want to come up against in the groups and we have had them twice in the last three years.
"They have an unbelievable squad. From one to 15 and their replacements, every other player in their squad is a good player.
"We have to be confident going in. They are going on 50 home games in a row that they haven't lost there.
"We will obviously look at them a bit but the focus needs to be on us and what we do.
"It was a very good win for us [against Zebre] and we desperately needed a bonus-point win in the RABO and they were a very physical side and we were happy to get those points at that time in the competition.
"But now focus switches to the Heineken Cup and we continue our rivalry with Clermont."
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