Munster boss Rob Penney stated his side were working to improve their high penalty count after their victory over Saracens on Saturday.
Ronan O'Gara kicked five penalties in Munster's 15-9 win at Thomond Park, but the home side conceded 18 penalties of which Saracens fly-half Owen Farrell missed four shots at goal.
"They are all 'must-win' games to be fair. We are in a tough pool. But Sunday's game is a must-win," said Penney.
"It is something we have been really focusing on, is our discipline and our work with the referees," added Penney.
"We got to a point where we conceded four penalties last weekend and I think we were up at 18 or something this week.
"Both sides defended so well and the pressure of the occasion probably didn't let the skills unfold as well as both sides would have liked," he added.
Saracens boss Mark McCall was left disappointed by his team's performance, citing his side's losing bonus point as a small consolation.
"We were well below our best tonight. It was a disappointing performance, overall," said McCall.
"We got off to a poor start and Munster were obviously very motivated. We lost a couple of set-pieces during that time. It gave them a lot of momentum.
"It was a frustrating kind of game because when we did have possession they were quite happy to give penalties away.
"The penalty count was huge against them. It was some consolation that we got a bonus point at the end."