The Latics have turned their attention away from their desperate survival bid for a few days as they prepare to face Manchester City at Wembley in the club's first FA Cup final on Saturday. When they return to league action against Arsenal at the Emirates on Tuesday, they could be six points adrift with only two matches left to play.
"Throughout the season the FA Cup's been excellent for us. We always seem to build momentum from it and hopefully we can do that again," he said.
"If you go and win the cup I don't think you'll have a higher high in football, and that's obviously going to have a positive effect on the team."
Things would have been significantly rosier had Wigan beaten Swansea on Tuesday but defensive blunders turned a 2-1 lead into a 3-2 defeat. The Latics' despair was obvious but McArthur insists they can put that behind them and focus all their attention on the cup final.
The midfielder said: "We've done it all season. It's been a really good distraction for us. We've built momentum from the FA Cup and hopefully we can do it again.
"We want to win the cup and we want to stay up. It's three massive games and we feel we can go and do the club justice and try to win the FA Cup first."
Wigan have lost their last seven games against City without scoring but will take confidence from the most recent meeting three weeks ago when their opponents needed a late Carlos Tevez goal to triumph at the Etihad Stadium.
"We know it's a big occasion but it's just another match," said McArthur. "We've played against Manchester City this season, we've not beaten them but away from home I thought we were sensational.
"It was one of our best performances of the season and we narrowly lost. So hopefully we can put that performance in with a better result."It's always good to be an underdog. Staying up as well, everyone expects us to go down, which we like. We like to try to prove people wrong, and hopefully we can do it this year again."