A devastated Giteau played just 25 minutes of the World Cup final before the independent concussion consultant stepped in to prevent him from getting back on the field.

Giteau played no further part in the final after he was knocked out in the first half when trying to tackle New Zealand giant Brodie Retallick and he had to sit on the sideline as the All Blacks secured a 34-17 triumph.

It was a shattering end to Giteau's resurrected international career, which was only revived when the ARU overhauled its eligibility rules this year to allow certain overseas-based players be available for Wallabies selection.

But the fairytale comeback was cut short as Giteau struggled to get to his feet after his tackle went wrong.

World Rugby has introduced concussion protocols to have video footage available in the medical room for an independent doctor to make a call on whether the player should be allowed to return to the field.

Giteau's injury was the second massive blow to the Wallabies in the first half, with lock Kane Douglas also being forced out for the rest of the game after damaging ligaments in his knee.

Giteau was able to run off the field unassisted and appeared to have shaken the symptoms, but he let his frustration and emotion out at half-time.

"He [Giteau] was not happy that he was ruled out of it. They ruled him out within 30 seconds, I'm not sure how that one worked out, but that's the way they did it," Cheika said.

"The medical referee made that decision, that's how he interpreted the situation. Gits gave me a gobful at half-time as to why he was off. But our hands are tied, there's nothing we can do about it."

The double injury blow added to the Wallabies woes in the first half as they struggled to get any possession or field position.

Douglas went down when he fell awkwardly after trying to catch the ball from the kick-off, with his leg snapping back underneath him.

He will have scans to determine the extent of the damage, but it is hoped he will be available to start the Super Rugby season with the Queensland Reds next year.

World Rugby has been trying to address the concussion issue by introducing strict return to field protocols.

Players must complete a series of cognitive, balance and memory tests as well as having an independent consultant reviewing footage of the incident and making a call on whether the player is fit enough to play again.

Giteau's incident was perhaps the biggest test for the protocols so far.

The player's instinct is always that they are fit enough to play on because of their desire to serve the team.

The independent consultant has been put in place to prevent any clouded judgment and uncertainty, but the system is still being tweaked.

The Wallabies did well to cover Giteau and Douglas' absence, with Kurtley Beale and Dean Mumm being injected.

The Wallabies scored 14 unanswered points in the second half to get within four points of the All Blacks, but the defending champion New Zealanders kicked into another gear and scored a late try to seal their win.

Cheika praised his side's courage and said injuries were not the reason for the Wallabies downfall.

"Obviously it's not ideal, but the guys who came on filled the spots. Dean Mumm played in Sydney when we played New Zealand and played very, very well.

"And Kurtley Beale, I thought, was outstanding when he came on. You want to have the depth there so you can launch those rotors on maybe a little bit later in the game when there's a bit more fatigue all round, but I've got no complaints.

"Beale's probably one of the best players we've had, either starting or off the bench, in the whole tournament."

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