O'Neill was a conspicuous absentee from the Roar's match-day squad, with Fowler revealing after the 4-3 win that the club had been told he was ineligible due to being unavailable for Australia's under-23s.

That was despite City having Lachlan Wales and Nathianiel Atkinson on their bench - two Olyroos regulars who weren't named in the squad to play a three-game friendly tournament this week in China.

AAP understand's O'Neill's omission from the Olyroos' squad was due to a travel issue.

Wales and Atkinson, as well as Adelaide's Riley McGree and Perth's Brandon Wilson, are all under investigation for an alleged incident last March in Cambodia while on Olyroos duty.

None of the four was named in the squad. But, it's unclear if they have simply been overlooked or are ineligible due to the ongoing investigation into their off-field behaviour.

McGree played most of Adelaide's 3-1 win over Central Coast on Saturday in Gosford and Fowler suggested it wasn't fair he had to omit O'Neill when others were allowed to play.

"We were told we couldn't play him because he was meant to be with the 23s," Fowler said.

"I think next time Aiden goes away with the under-23s I'll just tell him to misbehave so he can miss future squads and he can play in the A-League.

"We've seen a few players playing in the A-League this weekend that shouldn't have been playing."

The outcry isn't the first, amid controversy over the A-League's decision to continue with games during international periods, due to fixture issues with the addition of 11th team Western United.

The 2019-20 season kicked off during an international break - a decision Sydney FC captain Alex Wilkinson labelled "pretty average" before the season.

Despite O'Neill's enforced absence, Fowler's team overcame a 3-1 deficit in a thriller against high-flying City.

Socceroo Jamie Maclaren, who had been overlooked for Australia's World Cup qualifier against Jordan due to a hamstring injury, started and scored a hat-trick against his old club.

But Irish striker Roy O'Donovan scored a hat-trick of his own - including two penalties - as the Roar claimed their first win of the season.

City remain top on 13 points, however, with second-placed Western Sydney not playing this weekend and Western United suffering a shock 1-0 loss to Newcastle on Saturday in Geelong.

Champions Sydney made the most of that slip-up to move to second on the ladder with a come-from-behind 2-1 win over Melbourne Victory in the first 'Big Blue' of the season.

Captain Ola Toivonen put the struggling Melbourne team ahead but they couldn't hold on at Kogarah, with Adam Le Fondre and ex-Victory striker Kosta Barbarouses on target for the Sky Blues in the second half.

Australian Associated Press