"It's been quite incredible and I don't know whether we'll ever see the likes of it again," he said. "The other football clubs around the world on the same level have had their ups and downs, but United just keep getting bigger and bigger.
"I coached against them in 2000 and I thought they were massive then. If anything, in the last 13 years, they've become a bigger club on and off the field. It's unique, unprecedented, and unlikely to be matched again."
David Moyes also spoke about the quality of the A-League, saying: "There's no reason for Australian football not to become a major league itself.
"I know some of the Australian players from the past. Tim Cahill was one of my players. Obviously he’s not playing this game but I know their qualities.
"I also I know Lucas Neill from when he had a short spell at Everton. I’ll sure they’ll be up for the game. If you're picking the best from the A-League then we know it's going to be a big test for us."
The All-Stars representatives were speaking to footballaustralia.com.au.