The Mariners did not make life easy for the Sky Blues, who went ahead via Milos Ninkovic's first-half header but were pegged back level by Jake McGing eight minutes from time in Gosford on Saturday.

That was before substitute striker Simon executed a dramatic dive to head home Paulo Retre's deflected cross in the 93rd minute, ensuring Graham Arnold's side go eight points clear at the summit with three rounds remaining.

It was a frenzied end to a largely dreary affair that showed Retre can play at right-back and the club cannot afford to lose Ninkovic.

Retre's perfectly weighted cross picked out the Johnny Warren Medallist with precision, and his second assist was quality to help Sydney to a first victory in five games against a struggling side that have proved a nemesis this season.

The ninth-placed Mariners, still reeling from coach Paul Okon's sudden midweek resignation, sat back early and lacked the mettle in caretaker coach Wayne O'Sullivan's first game in charge.

One of the sharper performers, Danny De Silva, was subbed off at halftime with a hamstring complaint.

Retre, filling in for the still-absent Michael Zullo, released Bobo and the Brazilian striker forced a fine save from Ben Kennedy.

Fed by Alex Brosque, the 25-year-old then caught the Mariners' defence too high with a cross that picked out Ninkovic

As the rain started, Josh Rose executed an excellent piece of defending to stop Sydney doubling their lead.

But the visitors lacked urgency and their best chance to kill the game off ended in an inexplicable miss from Bobo, the golden boot leader lashing wide after Jordy Buijs played him in one-on-one in the box.

The Mariners pressed higher and Andrew Hoole squandered a golden opportunity for a late equaliser before some superb build-up play from Pain and Wout Brama allowed McGing to prod home in the 82nd minute.

A late Mariners penalty appeal may even have produced a winner, however Chris Zuvela was deemed to have got to the ball when he brought down Pain with six minutes to go.

But Retre was at the ready for another ball in, and Simon willing to oblige.

Australian Associated Press