Central Coast Mariners secured their first win of the A-League season by defeating reigning champions Sydney FC 2-0 on Friday.

Paul Okon's side ended a five-match winless start to the campaign, with goals from Andrew Hoole and Jake McGing putting Sydney's place at the top of the table under threat.

After Luke Wilkshire and Alex Wilkinson missed the target for Graham Arnold's side, the Mariners struck on the counter-attack in the 19th minute and Hoole guided a cool finish past Andrew Redmayne.

Central Coast doubled their advantage 10 minutes after the restart when McGing powered a header from Hoole's right-wing cross in off the underside of the crossbar.

Sydney pushed for a route back into the game and Wilkinson struck the upright with a header before Alan Baro, who made a number of important tackles throughout the match, was shown a second yellow card for a foul on Matt Simon with six minutes remaining.

Mariners goalkeeper Ben Kennedy did not have to make his first save until after his side were reduced to 10 men, the hosts holding on for a second victory in 13 league fixtures that leaves the door open for Newcastle Jets and Melbourne City to move above Sydney.