GWS coach Leon Cameron concedes his inconsistent AFL side aren't good enough to be in the top eight, having squandered a chance to clamber into the finals mix in a 18-point loss to Hawthorn at the MCG.
The 10th-placed Giants, who next face ladder-leading Melbourne, looked set to clamber above Fremantle and Richmond while banking a percentage-boosting win after booting Sunday's opening four goals.
But the Hawks seized momentum in a fashion as striking as Tim O'Brien's mark-of-the-year contender then held their nerve during a tense finish to triumph 13.12 (90) to 11.6 (72).
Dylan Moore booted four goals, including two clutch efforts in a 79-second burst that sealed the win, while 2018 Brownlow medallist Tom Mitchell had a game-high 40 possessions.
Callan Ward trimmed Hawthorn's lead to just five points late in the final quarter of the topsy-turvy tussle, only for a composed Moore to slot his set shot with a tick over three minutes remaining.
Moore snapped another goal moments later, putting the result beyond any doubt.
"It's disappointing that we served up some of that inconsistency ... we went back into our shells a little bit in the last quarter," Cameron said.
"With the gap (between the team's best and worst) still being a little too big, we sit outside the eight for a reason.
"Bridge that gap, then you deserve to be there ... we're not good enough to be in the eight yet."
The contest was on the Giants' terms in the early stages of their first 'home' game since escaping Sydney's growing COVID-19 cluster.
But their slick ball movement and superb pressure, having been hallmarks of the youth-fuelled resurgence that followed a 0-3 start, dried up after quarter-time.
"It'd be disappointing if we used that (relocating to Melbourne) as an excuse. We had an eight-day break," Cameron said.
"Hawthorn were on a seven-day break
"They outworked us.
"We just looked lethargic at times with our ball movement."
GWS went 47 minutes without kicking a goal as Hawthorn built a 22-point lead.
Hawks coach Alastair Clarkson clattered a water bottle when Daniel Lloyd ended the Giants' drought in the third term.
Stand-in skipper Toby Greene, unusually quiet throughout the opening half, booted two quick goals as he and fellow stars Lachie Whitfield and Josh Kelly ignited a GWS comeback.
Hawthorn's buffer was just three points at three-quarter time but they repeatedly steadied when challenged, extending some promising post-bye form.
"We were really disappointed with our first half of the year," Clarkson said.
"We needed to fix some things up with all areas of our game."
Substitute Shaun Burgoyne, who is set to become just the fifth man in history to play 400 VFL/AFL games when he tackles former side Port Adelaide next week, entered the fray at three-quarter time.
Chad Wingard (hamstring) is in doubt for the clash with Port, while Denver Grainger-Barras's debut ended in the fourth quarter because of a head knock.