"It was an honour to play for your amazing team that drew with the Demons," the former Westlife singer said as he greeted autograph hunters at the final whistle.

"It was awesome. I've played a few games in the last few weeks but nothing like that."

The trial match against Blacktown Demons was Sydney's first of the A-League pre-season ahead of the league kicking off on August 15.

The Sydney side included another ring-in, US college student Matt Taylor who partnered McFadden up-front for the final 20 or so minutes of the 0-0 draw.

Socceroo legend John Aloisi did not play as he is getting back to full fitness.

McFadden - dubbed B-Mac by fans - had a half chance late in the game after midfielder T-Mac - Terry McFlynn - played a ball through but the 28-year-old was marginally too slow to get on the end of it.

The travelling Sydney fans' chant of "You're just a poor Robbie Williams" and "You're Just A Fat Ronan Keating" was greeted with good humour by the former boyband star who clearly enjoyed his brief spell on the park.

"The Demons were a good side. I was very surprised. They gave Sydney as good as they got. It was hard out there. Intense," said the Dubliner who now lives in Sydney with girlfriend and singer Delta Goodrem.

McFadden's cameo was described as "outstanding" by a tongue in cheek Sydney FC coach John Kosmina after the match.

A film crew from TV reality show Football Superstar (on Foxtel's FOX8 channel) was there to document the singer's appearance at Gabbie Stadium in front of around 2500 fans.

Sydney FC have also been involved in Football Superstar, with coach Kosmina a judge on a show that's been dubbed "Football Idol".

McFadden is one of the two presenters of the programme, alongside former Matilda Amy Taylor.

Sydney's next trial match is on Thursday night against Sutherland Sharks at Seymour Shaw Park.