That means Petkovic will miss Friday night's match against Brisbane Roar, even if the FFA disagrees with Williams' original dismissal. The match review panel, which is independent of the governing body, had rejected the club's plea to have the decision overturned.

In order for a red card to be rescinded, it must be deemed an "obvious error" – in that there is zero ambiguity about the decision. As the Serb made high contact on Fabio Ferreira with his challenge in the 87th minute, the MRP dismissed the appeal.

However, the FFA offered a quasi-endorsement of the Sky Blues' unsuccessful claim, outing Williams from refereeing duties this week.

"Like everyone in the game, referees are accountable for their performances and decisions,"  A-League boss Damien de Bohun said. "The referees come under enormous scrutiny by the public and media, as well as the official reviews of assessors. In the view of the director of referees and that of the assessors, the decision by Ben Williams to show a red card to a Sydney FC player in last night's FFA Cup match was not warranted."

De Bohun acknowledged that referees needed to improve, just as playing and coaching standards have lifted notably in recent years.

"Accountability is part of improving the standard of refereeing in the A-League," he said. "If a player is dropped, the coach will work to get the player back in form as quickly as possible, and referees are no different."

Sydney FC chief executive Tony Pignata was left stumped as to how the FFA could agree with the appeal but was left powerless to do anything about it.

"Everyone knows the decision is wrong. So why is Nikola not playing? That's what we'd like to know. We need to move with the times. We all make mistakes, which the FFA rightfully admits, but it doesn't help Nikola's case," he told Fairfax Media. "Basically, the MRP is hiding behind the fact that they think a card of some sort was warranted. But even then, we all know that the difference between a red and yellow is huge."

Pignata said he would now push the FFA to work out a way to ensure a repeat of this scenario is avoided in the future.

"People may say I'm disappointed just because it's Sydney FC, but the truth is that this could happen again," he said. "That would be especially concerning. We need to make sure it will never happen to anyone else."

The club was initially confident that the match review panel would agree with their appeal and reject the one-match suspension.

"We really believed we had a good case for an obvious error appeal. We thought it would be upheld," Pignata said. "Now we're going to have to cop it, even if we don't like it, and the FFA agrees with us."

Pignata sat on the Sydney bench for the duration of the match and was only metres from the incident in question. He said nobody on Sydney's bench flinched – and neither did anyone on Adelaide's.

"There was nothing untoward from Nikola. Nobody saw a thing that would warrant a reaction. The Adelaide bench didn't get up – they just followed the play, as Adelaide went forward. We all did," he said. "When it was pulled back, and a red was shown, we couldn't believe it."

As a former chief executive of Football Federation Victoria, Pignata has had a close involvement with referees for some time, and while he agrees they must raise their standards, he is not convinced making them full-time will make them better.

"I don't know if full-time referees are the answer but the standard needs to get better as the A-League gets better," he said. "I understand we're all human, we all make mistakes, but we need to have better consistency. There's a lot of money, passionate fans and careers at stake. We all have to move in the same way and refereeing needs to lift as well.

"I think the immediate solution is to get the best referees on every week rather than being selected on rotation. The best five should referee every game and if they don't perform, they get relegated out of that five and have to work hard to get back in."