The champions appeared headed for a much-needed three points with 20 minutes remaining thanks to Rhyan Grant's lone strike early in the second half.

However the match turned on a single moment when second-half substitute Patricio Perez attempted to round Sydney custodian Reddy only to tumble to the ground under the challenge.

Reddy was dismissed and debutant Perez had no trouble converting from the penalty spot despite a lengthy wait as substitute goalkeeper Ivan Necevski entered the fray.

The home side protested the penalty award vociferously and subsequently appeared to lose their focus earning three cautions in as many minutes while the Mariners took a stranglehold on the match and could easily have snatched a winner.

Indeed the lively Perez put a header past Necevski only to see a potential winner ruled out for offside.

Sydney FC coach Vitezslav Lavicka was unusually animated on the sideline following the decision, and although reluctant to speak at length about the incident the Czech confirmed the club will appeal the red card.

"I am disappointed and I am very upset, I can't say nothing more but we will make an official appeal," he said.

The spotlight will surely fall on Perez should Sydney be successful in their appeal against Reddy's dismissal and automatic one-match suspension.

Replays suggest there was minimal contact between Reddy and the Mariners star off-season recruit meaning the A-League's regulations regarding simulation, introduced at the start of last season, could be utilised against the Argentinian.

The regulations allow for the A-League match review panel to sanction a player where undetected simulation has led to a referee awarding a penalty or the dismissal of an opponent.