Central Coast got their stuttering title defence back on track with a hard-fought victory over the Sky Blues in Gosford.
A sublime 26th-minute free-kick from recent addition Kim Seung-Yong for Central Coast was cancelled out by Richard Garcia's second-half equaliser.
But Mitchell Duke's third goal of the season, his first against the Sky Blues, saw the Mariners rebound from their mid-week loss to FC Seoul in the AFC Champions League.
Sydney, who have yet to win in Gosford since August 23, 2008, have now lost all three games to the Mariners this season with the result moving the Mariners to 30 points, leap-frogging their opponents into fifth position.
In an enterprising start to the game Duke and then Sydney's Corey Gameiro had early chances.
Gameiro was lively for the Sky Blues as the Mariners defence struggled to cope with Sydney's direct style early on.
Despite plenty of runs into the penalty area, the Mariners had their first two meaningful attempts just before the opening goal.
After 22 minutes Kim forced Vedran Janjetovic into a save before the 26 year-old goalkeeper blocked Joshua Rose's header from the left channel after a cross from Mile Sterjovski.
Central Coast eventually found a way past Janjetovic, with Kim netting his first goal for the club just four minutes later, curling his free-kick over the Sydney wall.
In the closing stages of the half, Italian World Cup winner Alessandro Del Piero came into the game with two shots on goal.
Veteran Del Piero started to exert his influence on the game winning a free-kick when he was fouled by Anthony Caceres after 54 minutes.
Sydney fans thought they had an equaliser before the Italian’s free-kick was spectacularly saved by Mariners shot-stopper Liam Reddy, who parried the ball onto the post but Sydney continued to turn the screws on attack.
Garcia's goal just after the hour-mark was one of finest finishes in some time on the coast as he fired home from near the right-hand by-line on a tight angle.
The game continued at pace with Sydney's enthusiasm offering the Mariners chances on counter-attack.
Duke had an opportunity to restore Central Coast's lead on 68 minutes but he was denied by the oncoming Janjetovic.
Soccceroo Duke was rewarded for his persistence when he thundered home to put the Mariners ahead with 15 minutes remaining.
Both sides attack with vigour late on giving the hearty crowd on a wet day plenty of value for money and a late Del Piero free-kick was deflected away as the Mariners clung on.