Adam Le Fondre struck twice in the first half to condemn Mark Rudan's side to their third consecutive loss and send the Sky Blues two points clear of Melbourne City.

"It wasn't our best performance with the ball but I think it was our best performance defensively," Sydney coach Steve Corica said.

"I think a clean sheet is very important. We had a big trip last week to Perth and obviously another trip down here this week so I think the boys were probably a little bit flat - they looked a little bit flat.

"But full credit to them, they worked extremely hard defensively, kept a clean sheet."

Sydney's day was made difficult before it had even begun, with Milos Ninkovic ruled out before kick-off through illness and replaced by Anthony Caceres, while United benched striker Besart Berisha in favour of Scott McDonald.

Western United started well, but Rudan was left to lament a drop-off in intensity after a pause in play 17 minutes into the game, when Sydney defender Ryan McGowan was down with a bleeding nose after a head clash.

"From a set piece they were able to get their first and they got their second again from a lapse in concentration," Rudan said post-match.

"I wasn't happy with the lack of intensity particularly after McGowan went down because I think that's when things turned around - they just lifted and we seemed to be second to everything as well."

As the first half went on, the Sky Blues seized control and opened the scoring in the 27th minute through Le Fondre.

Midfielder Alexander Baumjohann looped a potent corner kick to the back post where the Englishman comfortably saw off Connor Chapman and headed home.

United's best chance of the half came when Dario Jertec tried his luck from distance in the second minute of added time but saw his shot go skidding past the post.

Two minutes later, Brandon O'Neill played through Baumjohann down the right hand side, with the German cutting the ball back for Le Fondre, who buried his second goal to strike a hammer blow to the hosts on the stroke of half-time.

United largely looked toothless and were unable to score for the third consecutive week, with Greek international Panagiotis Kone forcing a rare save from Andrew Redmayne in the 84th minute, while Dylan Pierias had a shot blocked three minutes later.

While Sydney were unable to increase their lead, they held firm defensively for a well-worked 2-0 win and a sixth triumph from seven matches.

Australian Associated Press