GREATER Western Sydney has withstood a furious Collingwood fightback – and a score review controversy – to win by four points and qualify for a historic maiden AFL Grand Final.

The underdog Giants led by a match-high 33 points almost six minutes into the final term, were dominating proceedings and would have thought the game was well in their keeping. 

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At that stage, the Magpies had kicked three goals in more than three quarters of football, yet somehow they almost conjured one of the most remarkable comebacks in finals history.

A Jaidyn Stephenson goal kickstarted the drama, but it was Josh Thomas' major at the nine-minute mark – the second of four straight from Collingwood – that provided the talking point.

Thomas' shot appeared to be clearly touched by defender Lachie Keeffe, but play resumed in the middle after a short delay, meaning the Pies were awarded maximum points.

It is understood the reviewers in the AFL's new ARC set-up followed the correct process and conducted a 'silent review' of the vision before the ball was bounced. However, they decided there was insufficient evidence to declare beyond reasonable doubt that the ball had been touched. 

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Fortunately for the AFL, the Giants narrowly hung on by an 8.8 (56) to 7.10 (52) scoreline in a classic encounter in front of a black and white-dominated MCG crowd of 77,828.

Richmond, the 2017 premier, awaits at the same venue in a week's time.

After all the fuss about Toby Greene's Tribunal outcome, the Thomas incident would have left GWS chief executive Dave Matthews' blood boiling.

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There were still 19 points the difference at the time of Thomas' goal, but Collingwood never stopped coming and had a series of chances to gobble up its deficit.

A mid-air strike from Chris Mayne slashed the GWS advantage to 13, then Thomas snapped a brilliant goal to make it only six points.

That was the game's final major, but the Pies will rue Ben Reid's errant set shot, a Mayne attempt that was initially called a goal then correctly ruled a behind on review, and a heartbreaking Taylor Adams poster.

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The Sherrin was parked almost permanently in Collingwood's attacking 50 in the dying minutes, and the last opportunity came via Brayden Maynard.

Maynard blasted the ball to the top of the goalsquare, only for Giant Sam Taylor to elevate and fist the ball away rather than try to mark.

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Time eventually ran out for the Magpies, whose bid for back-to-back Grand Final appearances and a sixth since 2002 fell agonisingly short.

Earlier, Greater Western Sydney trailed Collingwood by three points at the main break in what was its third preliminary final in four seasons despite leading in most of the key categories.

The combined half-time tally of 37 points – the Pies led 3.2 to 2.5 – was the lowest in a VFL/AFL final since the 1928 semi-final between Collingwood and Melbourne.

Either the Magpies were about to make the Giants pay, or the men in orange were finally going to break the shackles.

The game-turning moment came in a hurry.

Jeremy Cameron chipped the Sherrin inside 50, then Bobby Hill – in his eight AFL match – hunted it to the boundary, and a series of slick handballs ended with Brent Daniels curling his kick in for a goal.

That was Daniels' second touch in the chain and came via a quick-thinking Jacob Hopper dish that released him.

Barely four minutes had passed in the second half, but GWS was in front for the first time since the 18-minute mark of the opening quarter in what had been an MCG cliffhanger to that point.

The Giants never surrendered the lead from there, going on to kick five goals to none in the third term.

It was their second straight win on the road, after upsetting Brisbane by three points at the Gabba a week ago.

Daniels' major was the first of four for the Giants before the third term reached its halfway mark, before a costly Jack Crisp turnover seemed to have sealed Collingwood's fate.

Crisp elected to go sideways into the corridor and gifted the ball to Daniel Lloyd – and in a matter of seconds Cameron was lining up for, then kicking, his second goal.

Cameron was excellent in what was an engrossing battle with Darcy Moore, with his two magnificent set shots from not far inside the boundary at the city end proving incredibly valuable.

GWS may have almost blown it, but ultimately richly deserved this result.

Nick Haynes and Taylor were resolute down back, especially with co-captain Phil Davis (calf) going down in the first quarter and spending most of the game up forward thereafter.

Josh Kelly came up big in the second half – important in the absence of Stephen Coniglio, Lachie Whitfield, Callan Ward and Greene – and Zac Williams was great from the get-go.

Young Giant Harry Perryman played arguably the game of his life, too.

There will be reinforcements next week, including Greene, Whitfield and maybe Coniglio, but this team has proven beyond doubt its character is every bit as valuable as its star power.

COLLINGWOOD     2.0     3.2     3.5     7.10     (52)
GREATER WESTERN SYDNEY     1.3     2.5     7.7     8.8     (56)

Stephenson 2, Thomas 2, Reid, Elliott, Mayne
Greater Western Sydney:
Cameron 3, Finlayson 2, Taranto, Williams, Daniels

Collingwood: Crisp, Grundy, Pendlebury, Maynard, Wills, Howe, Treloar
Greater Western Sydney:
Williams, Taranto, Haynes, Perryman, Cameron, Kelly, Finlayson

Greater Western Sydney:
Davis (calf)

Reports: Nil

Umpires: Stevic, Stephens, Meredith 

Official crowd: 77,828 at the MCG