Mercurial Sydney sharpshooter Nick Davis looms as the Swans' x-factor for next month's AFL finals following his best-on-ground performance against the Kangaroos.

The gifted 25-year-old is one of the least predictable weapons in Sydney's potent forward line but was pivotal in the opening half of his team's 15.11 (101) to 9.10 (64) win at the SCG.

Davis booted five goals, including four majors in the opening half, as Sydney raced to a 37-point quarter time lead and was never threatened against the finals-bound 'Roos .

The victory sealed the double chance for Sydney and Davis' performance in a forward line including Barry Hall, Michael O'Loughlin and Ryan O'Keefe will cause sleepless nights for opposition defensive coaches.

Sydney coach Paul Roos was delighted to see another key piece of his forward line firing so close to the finals.

"I thought at some time he was going to have a break out, while he had not been having a great four quarters, he had been in some good form over the last few weeks and just a fraction from being one of the really, really good players," Roos said.

"So it wasn't surprising for him and he was the one who bobbed up today and kicked five and did a really good job, particularly earlier."

The 2002 grand finalist with Collingwood has polled nine Brownlow Medal votes in 107 games before this season, a moderate return considering his polished skills.

Davis only had two touches after halftime but the damage had been done as Sydney led by eight goals at the main break and the Kangaroos head back to Melbourne with their tails between their legs.

The men from Arden Street have now suffered successive losses to heavyweights St Kilda and Sydney and on this form won't be making much of a dent in September.

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