Influential Australia flanker Rob Valetini misses out on the third and final Test against the British and Irish Lions as the Wallabies look to avoid a series whitewash in Sydney on Saturday.

Valetini made a significant first-half contribution in the 29-26 second Test defeat in Melbourne but was withdrawn at the interval and is now not involved in the matchday squad as he manages a calf problem.

Elsewhere, head coach Joe Schmidt makes a handful of changes as the Wallabies attempt to recover from a "gut-wrenching" late defeat in Melbourne.

The experienced Nic White, who has announced his retirement from international rugby, starts at scrum-half, while imposing prop Taniela Tupou comes in at tighthead for his first appearance of the series.

After a meek first Test performance in Brisbane, the Wallabies were markedly improved a week later, rushing into a 23-5 lead before the Lions came back to seal the series in dramatic fashion at the MCG.

"It was an incredibly deflated group (after the defeat)," Schmidt said.

"And Tuesday it was tough to get them off the campus. It was almost like a grieving process over the first few days. But they have started to gather momentum in the back half of the week and will be ready to go again on Saturday."

Dylan Pietsch replaces the injured Harry Potter on the left wing, while back row forward Carlo Tizzano, who was involved in the controversial ruck at the end of the game involving Lions flanker Jac Morgan, is not part of the squad.

Tizzano has been criticised for his reaction to the collision with Morgan, and Schmidt says he has endured a difficult few days following the incident.

"He's copped a lot of online abuse this week," added Schmidt.

"In defence of Carlo, just over 54 Gs of force - direct force - went through his neck, which is enough to cause serious injury, although not to a rugby player as well conditioned as Carlo.

"But he's probably left to take a deep breath. I think we are all aware of Newton's third law - for every reaction there is an equal and opposite reaction. When that force hits him and the speed of his head collapsing down, he recoiled out of the back of the ruck.

"I don't think he wanted to recoil like that but that's the nature of force. I think for Carlo it's better he sits this one out.

"We weren't sure about him on Tuesday - he was pretty sore - but he was great today and back to the irrepressible character he is."

Schmidt revealed White spoke to him last week about his retirement, but said his selection is not based on sentimentality, citing the strength of his kicking game in what are expected to be wet conditions.

"I'm not a sentimentalist - it's a Test match," Schmidt said.

"It's a decision we made believing Nic can do the job. Nic has an excellent kicking game and the confidence of the players, he played well against Fiji and against the British and Irish Lions for the Western Force."

As for Valetini, his absence was described as "precautionary", with Schmidt citing Australia's busy international schedule following the Lions series.

"He's not right this week", Schmidt said. "It is the same injury and it just tightened up. It was precautionary bringing him off and it is probably precautionary not playing him this weekend."

While Valetini's ballast at the back of the scrum will be missed, the return of the massive Tupou will give the Wallabies a power boost.

The 23st Tupou has struggled for form and confidence of late, but has the potential to be one of the most destructive props in the game. He starts in place of the injured Allan Alaalatoa.

Schmidt said: "We are hopeful Taniela can bring us a real burst of energy, because I think one of the reasons we've made a few changes is that when everyone is as flat as they were, just bringing a few newer guys in it just freshens things up and those guys know it is an opportunity for them."

Australia: Wright; Jorgensen, Suaalii, Ikitau, Pietsch, Lynagh, White; Slipper, Porecki, Tupou, Frost, Skelton, Hooper, McReight, Wilson.

Replacements: Pollard, Bell, Nonggorr, Williams, Gleeson, McDermott, Donaldson, Kellaway.

British and Irish Lions: Keenan, Freeman, Jones, Aki, Kinghorn, Russell, Gibson-Park; Porter, Sheehan, Furlong, Itoje, Ryan, Beirne, Curry, Conan.

Replacements: Kelleher, Genge, Stuart, Chessum, Morgan, Earl, Mitchell, Farrell.