Maguire has vowed to bounce back from a disastrous slide in fortunes last season that let to speculation he may be sold this summer.
New United manager Erik ten Hag has insisted he will back Maguire and keep him as club captain, but the reaction of United ‘fans’ in Australia confirmed he has a lot of rebuilding to do.
Maguire had avoided a negative reaction in Bangkok and United’s first friendly at the MCG, but the centre-back was jeered during the start of Tuesday’s 3-1 victory against Patrick Vieira’s Palace.
The England international appeared to win over supporters with an impressive showing and the boos subsided during a first half that saw Anthony Martial score in a third successive friendly.
The reaction to Maguire from United supporters has left former defender Brown bemused, as the United Champions League winner suggests genuine fans will always back the players so long as they are giving their all.
"Look, Harry Magiure has a bad season, he doesn’t need me to tell him that,” Brown told sundayworld.com at a Bookmakers.com event.
"What I would say is no supporter should boo a player if he is out of form. That’s when he needs support and real fans should get behind a player who is trying his best.
"Maguire has been trying his best, but it just hasn’t been happening for him. We’ve all been there, I know I have. The problem is, when you play for a big club like United, the spotlight is one you.”
Maguire is determined to win over his doubters at United doubters after what he admits was a woeful year.
“Listen, last year was disappointing,” Maguire said. “As an individual I didn’t play well and as team we certainly didn’t play well.
“But a good career can last 10 to 15 years and you’re never going to have every year where it’s plain sailing and you don’t have any difficulties.
“You’re going to have to fight, you’re going to have setbacks and last year was certainly a setback for myself on my career path.
“But it’s behind us now and we look forward to the future and getting this club back to winning trophies, which is what it’s all about.”
Ten Hag has so far overseen a success pre-season campaign for United, with the high intensity training raising the fitness levels of the players he has inherited.
The demanding Dutchman’s fingerprints have been visible in the performances to date and his work at the club has impressed the squad.
“It’s been tough,” added Maguire. “The running has been hard but we’re really looking forward to the season.
“Everyone – the players, the club – know last year was nowhere near good enough but it’s a fresh start and we’ve got a big season ahead.
“Erik and his coaching staff are bringing their ideas and the first two games you’ve seen little glimpses of the principals.
“We’re working towards being ready for that first Premier League game, that’s what matters. Everything we’re doing now is building for that first game.”
Ten Hag has already indicated that Maguire and new signing Lisandro Martinez – who will be joining imminently from Ajax – will start the season as his first-choice central defensive pairing.