Sydney were up 3-0 at the break before piling on another two to make it a bleak night for Josep Gombau's men.

The Spaniard's radical selection changes - which saw key personnel benched - will be one of the talking points from the night.

But the big takeway was the influence of Mierzejewski who chipped in with a first half brace (14', 45') to help the reigning champions record their biggest derby and away win.

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"It was a really good game for us," the Polish international told Fox Sports post-match.

"It was not easy, of course, but the result is amazing and a victory for our fans.

"Now we have five minutes to celebrate and then we start to think about Friday's game against Melbourne City."

Sydney are now eight points clear at the top of the table and 17 points ahead of their derby rivals.

Captain Alex Brosque scored his first of the campaign (41'), before an own goal by young striker Lachlan Scott (53') and a rare strike by Brandon O'Neill (76') completed the humiliation.

Through it all, Mierzejewski was central to the drama, with two superb free kicks, one that added to Sydney's tally and the other that forced Scott to head into his own net.

Unbelievably It could have been worse. A handball by Mierzejewski saw a Michael Zullo goal chalked off, while some standout saves by Vedran Janjetovic stopped Brosque from increasing his tally.

Mierzejewski added: "As I said before the game, for us it doesn't matter if we play against Wanderers, Perth, Victory, Brisbane - with all respect to the teams - but we want to win and we expect to win every game. Doesn't matter, home or away."

Wanderers are now winless in eight.