A shock home reverse against Connacht has thrown Pool 3 wide open after Toulouse had done the hard work in beating Sarries 17-16 at Wembley in October and Sunday's clash carries extra significance as a result. Toulouse and Saracens are currently level on points at the head of the table but a second straight home reverse in Europe would see Sarries become overwhelming favourites to finish as top dogs the week after next.
Toulouse return to continental competition on a high having beaten French league leaders ASM Clermont Auvergne 19-12 on Saturday but Nyanga is convinced they will have to perform even better if they are to taste similar glory against Sarries.
"We are going into what is really a knockout game. And that wasn't the case against Clermont. The intensity of the game on Sunday will be a cut above," said Nyanga.
"Saracens are in the same category as Clermont in terms of quality, but there is a difference: Clermont came to Toulouse without any pressure on them and (because of what is at stake) that won't be the case for Saracens.
"We are aware that a victory against Saracens won't come easily and that the game won't be the same as what happened against Clermont. The challenge is different and we have to meet that challenge."
Victory over Clermont was a big boost for Toulouse given that they were well beaten by lowly Bayonne in their previous domestic fixture but Nyanaga has re-iterated his belief that there is no danger of any of his team-mates getting carried away.
"Today's truths are not tomorrow's," added Nyanga, who played in the 2008 Heineken Cup Final defeat to Munster but missed the 2010 showpiece win over Biarritz Olympique.
"We were better at the weekend but I don't like falling into complacency and we know we need to keep working. We won't drop into any sense of triumphalism. Now we simply put all our efforts into switching into Heineken Cup mode.
"We have shown that we are able to meet big challenges and we will need to show that again on Sunday. The win over Clemont may have re-assured us that we can win these big games but, at the same time, we never really doubted our ability."