The two teams meet in a high profile friendly on July 20 at ANZ Stadium before Postecoglou heads back to Melbourne to coach his club side Victory against Liverpool. 
 
And the attack-minded Melbourne Victory coach believes the nature of the United game means the All Stars' ability to pinch a famous victory is not out of the question.
 
“Why not! That’s what I keep saying,” he told au.fourfourtwo.com. "On a level playing field you’d probably say no. It’s almost impossible.
 
"But in a one-off game, particularly in this scenario, it’s what you want to go for.
 
“I think on both fronts, though, it’s important in both games that we show our league as a good standard. I’m really interested in the quality of our football as much as results.
 
"If Manchester United, and Liverpool, leave our shores and say, ‘you know what, they can play football’ that’s as much of a victory as anything else.”
 
Postecoglou has already coached against new United boss David Moyes.
 
Brisbane Roar hosted Everton in July, 2010 at Suncorp in a "Roar against Racism" friendly. 
 
Moyes's Toffees club survived a second-half scare to record a 2-1 win over the A-League outfit.
 
Postecoglou believes the weight of expectations will be the biggest challenge for the Scot now that he’s in charge of one of the biggest football brands on the planet.
 
“It’s not easy," said the Victory boss. "Everything is scrutinised and you’re expected to challenge for everything on offer. 
 
"And you can guarantee in that game against the All-Stars there’ll be a lot of attention from across the world as they scrutinise the new era.“If Sir Alex was still in charge possibly not so much.
 
“But I’m sure he’ll be prepared for that. I coached against him up in Brisbane. He seemed a pretty down to earth bloke and really focused on his coaching.”
 
For exclusive A-League All Star content ahead of the United game, get yourself a copy of August’s FourFourTwo Australia magazine (out July 11).
 
It features the full interview with All Stars coach Postecoglou as well as a chat with All Star defender Pedj Bojic.