And Williams, who will captain the Blues in the absence of British Lion Martyn Williams, is well aware of the cost of losing out on a place alongside Europe's elite.
"We have to go there and win, it's as simple as that," said Williams. "It's important both financially for the region and for the players that we are playing against the best sides in Europe.
"Training has gone well over the last few days and we are clear about what we have to do. It's about making sure we're in the Heineken Cup next season."
The Blues failed to qualify automatically for the competition by finishing as the bottom Welsh side in the Celtic League. They have been given the play-off chance however by finishing above the bottom placed Scottish and Irish regions (Borders and Connacht).
Viadana qualified for the tie after losing out in their semi-final play-off in the Italian league against Calvisano, but finishing above the other semi-final loser, Catania. The loser of Sundays showdown will go into the European Challenge Cup.