SYDNEY'S third straight loss to cross-town rivals Greater Western Sydney is the perfect game to sum up a disastrous start to the season. 

Just as they have in all five games this year, the Swans showed patches of outstanding form at the SCG, like the four goals they piled on in the opening four minutes of the game before GWS won a possession, but backed that up with long periods of substandard footy in the 42-point loss. 

The Giants steadied after the first-quarter onslaught, and clinically kicked the next nine goals of the game before half-time to stun the home crowd. 

After playing off for last year's premiership, the Swans are now 0-5 and staring firmly at the prospect of missing the finals altogether.

Full match details and statistics

Since the inception of the final-eight system in 1994, no team has lost its first four games, let alone its first five, and gone on to play in September.

Swans coach John Longmire said the defeat painted a perfect picture of his side's winless start to 2017.

"We jumped right out of the blocks but what good teams do, as in GWS, they came back and took their turn, and their turn was too long," he said.

"We needed to turn it quicker than we did, and it took until half-time until we addressed it and got it back on an even keel.

"We've been unable to sustain a competitive brand of footy for long enough over the course of a game. We're showing bits and pieces here and there, but the majority of the time we haven't been able to sustain it for the period of time that's required at AFL level.

"It's a combination of a number of different things and it all adds up to that inconsistent performance, and not being good enough for long enough."

WATCH: John Longmire's full post-match media conference

The Swans got no impact from Kurt Tippett, Isaac Heeney and Gary Rohan, who struggled to have an impact in their return from injury, with Tippett particularly quiet as a key forward and in the ruck. 

GWS big man Shane Mumford dominated the ruck with 62 hit-outs and took home the Brett Kirk Medal for best on ground. 

"It's only natural, they haven't played a lot of footy and that's just the way it is," he said.

"I thought Gary (Rohan) competed pretty hard but in the end you've just got to find a way.

"There's a number of blokes that have played a lot of good footy and regardless of what has happened previously, you've just got to dig in." 

Sydney are unlikely to have former co-captain Jarrad McVeigh fit to take on Carlton next week at Etihad Stadium after he pulled up with a tight hamstring at training on Thursday.

McVeigh hasn't played a game this season because of a calf injury but had been training solidly for the past fortnight before his latest setback.