MacPherson admits the trip was done on the down-low.
He told the Scottish Sun: "We did things very quietly. I didn't want any fuss made, we considered ourselves very fortunate to get the opportunity, so we told no one.
"It was fixed up for us through Martin Ferguson and it was a magnificent experience.
"We were taken into the inner sanctum at Manchester United and it was phenomenal. Sir Alex couldn't have looked after us any better.
"We arrived at around 9.30am and from then on Sir Alex was constantly by our side.
"Before we knew it we were standing at the side of the pitch, three yards away from the likes of Rooney, Giggs, Scholes and Berbatov.
"It was an experience I'll never forget, a day in the company of the best of the best.
"I thought we might get to meet Sir Alex and have a two minute chat, but he welcomed us with open arms and couldn't have been more accommodating. He went back to Old Trafford to do some business for an hour at lunchtime, but he insisted we stay at Carrington until he got back.
"We talked about different training ideas, coaching and tactics. Andy (Millen) and I drove back up the road having gleaned great information from arguably the best manager in the world."