Munster have contested two of the last three Heineken Cup finals, losing by a point to Northampton in 2000 and 15-9 to defending champions Leicester Tigers last May, but now find themselves in a potential three-way tie with Perpignan and Gloucester for the top spot in Pool 2 in the scramble for automatic quarter-final qualification.
"The game in Perpignan could decide whether or not we qualify for the quarter-finals," said Gaffney. "A defeat would not end our hopes, we could still make it through to the last eight, but we would need to score plenty of tries.
"The moment we came off the pitch on Friday night (after beating Ulster 42-10 to qualify for the Celtic League final against Neath) we said that nothing less than a win at Perpignan would be acceptable.
"However, Perpignan have started to score lots of tries and points and any side who can do what they did to Gloucester must have something pretty big going for them.
"I went to Perpignan earlier in the season with Jerry Holland, our team manager, and Stade Aime Giral is a very intimidating place, a tough place to go and win.
"That said, Munster have an excellent Heineken Cup record in France and going over there holds no fears for us.
"Perpignan are obviously a very strong all-round team and in fly half Manny Edmonds they have an exceptional No 10.
"I coached him for two seasons at New South Wales and he is a very good player. He had two Tests for Australia, against Tonga and South Africa, but perhaps was always a bit in the shadow of players like Steve Larkham. Nevertheless, we will have to watch him closely - he has already scored three tries in this season's Heineken Cup.
Munster are top of Pool 2 with three wins from their four games, they have scored 22 tries along the way, just one mort than their nearest rivals, Gloucester, who they face in their final Pool match next weekend.