Kilmarnock were forced to settle for a share of the points in the inaugural game at the Greenhill Road venue, before Saints were unfortunate to be held by Falkirk last week.
MacPherson knows the lack of wins will quickly become an issue if the situation is not rectified quickly and has targeted victory against Mark McGhee's men after taking the fifth-round tie back to Paisley.
"The longer you have to wait for it, the more people start talking about it," he admitted.
"We've only had two games here and drawn them both so, if you were being positive, you would say we are undefeated.
"The most important thing is that we are playing well, we are playing with confidence.
"I would be more concerned if there was a lack of confidence in the dressing room but they are a confident group of players with a real determination about them at the moment."
He added: "The players are settling in fine. I don't think they can complain about anything but, knowing what players are like, they probably will complain!
"It's night and day compared to what they had at Love Street. They are adapting to the surface well.
"They had half a dozen training sessions before the games and the players did comment that it was better playing on the pitch against Falkirk than it was against Kilmarnock. They are adapting to it and enjoying it."
The Saints players may be enjoying their new surroundings but MacPherson fears the brand new surface may also benefit Motherwell, whose own Fir Park pitch is currently in a dreadful state.
He said: "We are hoping home advantage will count for us but we know that isn't going to have a great bearing on it, considering what the Motherwell guys are playing on at Fir Park.
"They will be looking forward to coming here and Mark McGhee has already said that so we will have to contend with that.
