Saints travel to Stark's Park for the Sky Live midday kick-off knowing victory will secure a last-four meeting at Ibrox early next month, their fourth semi-final spot in the last eight years.
"My players are very motivated for this match," he told Sky Sports News. "We were very disappointed to lose the League Cup semi-final but we now have a great opportunity to get through here.
"Away to Raith Rovers will be a very difficult tie. They had a tremendous result in the last round away to Hibs, but we have prepared well this week and are looking forward to the tie.
"I know Raith are not in very good form at the moment as far as their league results are concerned, but in a one-off game they have proved just how dangerous they can be.
"To go to Hibs - we were there early on in the season and couldn't get a result - and get a result is very difficult. For them to score three goals away from home shows they have the firepower and quality in their side which can hurt you.
"With Celtic out of the competition it is wide open. They are the best team in the country at the minute so with them going out every club left in the competition will fancy their chances.
"And winning this trophy would be huge for the club, and this town. We haven't won a major trophy in 130 years so it would mean everything to the supporters, the club and the players.
"Opportunities to win things at clubs like ours are basically down to cup competitions and we have to make the most of that this season."
Watch Raith Rovers play St Johnstone for a place in the last four of the Scottish Cup live on Sky Sports 1 from midday on Saturday