The Sutherland-raised midfielder with a nose for goals has caused a stir since coming on as a late substitute in the match against Queensland Roar.
In the five minutes that he was on the field he did enough to be on the bench again in the next game at Newcastle Jets.
And after coming on as a 72nd-minute substitute for Bobby Petta he scored the winning goal with his first touch of the ball.
Then came his glorious strike against Melbourne Victory in his third start three weeks later that convinced club management that this kid was something special.
This week he was offered a two-year contract worth about $90,000 and next season he will be expected to play a key role in Sydney's drive to reinvent themselves after a hugely disappointing season that will see the club miss the finals for the first time.
Sydney's squad next season will comprise three elements: a group of the club's most talented young players, a core of established stars and four foreigners.
Gan, who is of Malaysian descent, is thrilled and honoured to have been asked to be part of the new Sydney.
“The boys helped me make the adjustment to A-League football,” Gan, 20, said.
“I guess that's what the youth league is for … to develop our skills and knowledge of the game and I've proved that all the youth boys can step up. I'm sure next season we will do wonders and be in the title race.”
Gan, who was voted NSW player of the year in 2008 after helping Sutherland Sharks win the premiership, took to A-League football like a fish to water.
Watching him move around with menace and poise in the middle of the park, it is easy to forget that he essentially is still a raw apprentice.
However the way he adapted so easily to senior football has surprised many people, not least his coach John Kosmina.
“At the start he got thrown in at the deep end and he was a bit overawed,” Kosmina said.
“But the kid's dead honest, he's intelligent. You can talk to him. He listens because he wants to learn.
“And he can run all day long. Gan can get from box to box quite comfortably and that's what we need.”
Gan, who is expected to start in Sunday's match against Wellington Phoenix at the Sydney Football Stadium, said he had no complaints about the role he has taken up in the team.
“Hopefully I've done enough to prove my position. I am an attacking midfielder because I love being where the action is. That's been my position all my life,” he said.
Gan said he still had a lot to learn and there was no chance he would be distracted or get carried away by his early success.
“I won't be a complete footballer until I learn how to play the game and have the knowledge of what the game is about,” he said.
“Being in the Sydney team with such experienced players makes me more confident of what to do, where to go and what runs to make.
“I need to improve on every aspect of my game and hopefully Sydney will help me achieve that.”
Gan said he could not speak highly enough of Sydney's senior players for making his transition from youth to senior football so smooth.
“Every one of the more experienced players took me under his wing and taught me what I needed to learn,” he said.
“Without their experience and knowledge I would not be here at this moment.
“I will always be grateful to all the guys like Steve Corica, Iain Fyfe, Terry McFlynn, Tony Popovic and of course Kossie.
“But you make your own luck and anyone can achieve what they want if they put their mind to it.”
So what are his ambitions as a footballer?
“I want to take it day by day and game by game. I'm not looking too far ahead. All I want to do is give 100 per cent every game,” he said.
Brendan Gan is also learning fast how to handle the media.