The 22-year-old has noticed a significant change in intensity on the training ground this week, boosted by a win against Glasgow Warriors in the RaboDirect PRO12.
But having lost to Racing Metro in their first Heineken Cup fixture, Butler admits his side cannot afford to fall further behind their opponents, who top Pool 1 with two wins.
And as a forward himself, the former Ireland U20 international knows he will have to take on an added responsibility when stepping out at Thomond Park tomorrow.
"There is a great buzz around the camp and everyone knows how important this game is," said Butler. "We are aware of how vital it is to win the game. If we lose we all know we could be out the competition so it is very much a must-win.
"We all had a look at their last few games. They had a good win against Gloucester so they will be on a high and we need to be prepared for that and it will be a tough task.
"Their set-piece is very good. They have the highest percentage of line-outs won in the Premiership so I think that is where it will be lost or won, in the scrum and line-outs, and me being a forward as well that is the most important area.
"Everyone knows its Heineken Cup week. Everyone is a bit sharper, on edge and we all know the importance of the week particularly looking at the previous seasons."
Both sides exited last season's competition at the quarter-final stage but with the weekend's win still fresh in the memory and home advantage in their favour, Butler is confident of victory.
"It was brilliant to get a win against Glasgow because we didn't feel we played to the best of our abilities against Scarlets the week before and we felt down so it gives us a boost," he added.
"The Munster support is always good and the atmosphere is electric so we hope we put on a game and get a win for the supporters to celebrate."
Guinness PRO12 Munster News
63x46.png){kind=logo}