Former Sydney FC goalkeeper Vedran Janjetovic was sent off as Western Sydney Wanderers let slip the lead to lose 3-1 to his old club in a thrilling derby at ANZ Stadium.

Janjetovic, who switched allegiances in a transfer that angered Sydney FC fans in December 2016, was shown a straight red card after he handled the ball outside the penalty area just moments after Oriol Riera had given the home side the lead from close range on 23 minutes.

Alex Brosque levelled the match in first-half stoppage time, flicking home the rebound from Joshua Brillante's drive that came back off the post before substitute keeper Danijel Nizic could react.

Siem de Jong scored to put the visitors ahead, arriving at the far post to score after Aaron Calver flicked on a 57th-minute corner, and substitute Jacob Tratt crashed a header home to seal a win that leaves Sydney FC just four points behind A-League leaders Melbourne Victory.

Meanwhile, Wanderers were left teetering six points above rock-bottom Central Coast Mariners, who succumbed to a 2-0 defeat at Wellington Phoenix earlier in the day.

Phoenix went into the game on the back of a 3-1 victory at Sydney FC and picked up where they left off as Louis Fenton pounced on the rebound from Mandi Sosa's shot and slotted the ball home after nine minutes.

Wellington dominated thereafter and doubled their advantage when Roy Krishna played in Sarpeet Singh and the forward calmly beat goalkeeper Adam Pearce with a side-footed finish.

The result left the Mariners still searching for their first league win of the season, while Wellington moved up to fifth in the table.