Sydney - England coach Eddie Jones on Thursday said he was targeting a 3-0 whitewash of Australia as a "dress rehearsal" for the next Rugby World Cup.
Jones said the 2019 World Cup in Japan was the ultimate goal for his England team, which he has steered to eight straight wins including a first series victory in Australia.
"We've treated this week like a dress rehearsal for the (2019) World Cup because that what we're always building towards," Jones said.
"To win a World Cup you have to win three big games in a row - we've won two so this third game is the most important game we'll play all year. It will be a good indication of where we are as a team."
England made only one team change for Saturday's game in Sydney with Northampton Saints flanker Teimana Harrison replacing No 7 James Haskell, who has a foot injury.
But the Wallabies have rejigged their battered team as they fight to avoid a 3-0 series wipeout - after winning all but three home games against England before this tour.
Jones and his Six Nations champions have held all the aces so far, winning the opening two games 39-28 in Brisbane and 23-7 last week in Melbourne
Jones, a former Wallabies coach, has vowed no let-up in intensity and is urging his England team to go all out to sweep Australia in their pursuit of becoming the top side in world rugby.
His counterpart Michael Cheika, a former team-mate at Sydney's Randwick club, has reshuffled his side in a bid to prevent another demoralising defeat.
He has turned to the play-making skills of Matt Toomua at inside-centre, brought in the hulking Will Skelton to partner the recalled lineout general Rob Simmons at lock and has powerful Fijian-born winger Taqele Naiyaravoro among his replacements.
Cheika has vowed to keep the Wallabies' attacking approach which has been negated by England's forwards-dominated game and emphasis on high kicks.
"Saturday's match against England is a real opportunity for the Wallabies to show the character I know they have on the field, for all our fans to see," he said on Thursday.
"We will continue to play rugby in our attacking style and we'll be aiming to do it with more consistent quality than we have in the first two matches."
It has been a dramatic reversal of fortunes for Cheika's men after the Wallabies reached the final of last year's World Cup against New Zealand in London and went into the current series ranked second in the world.
England now have leapfrogged Australia to number two behind the All Blacks on the back of their eight-match unbeaten run under hard taskmaster Jones.
But Jones is demanding England approach the 'dead rubber' Test the same away they did in the other games in the series.
"We want to be the best team in the world and we want to win the series 3-0," he said.
"If we want to be the best team in the world, we'll be thinking 3-0. We know Australia will come back, they're a well-coached, driven team. So we're anticipating quite a feisty encounter in Sydney."
Australia will have to find a way to counter England's strong set-piece and tidy up their discipline and errors under the tourists' concerted pressure.
Toomua will help inject some unpredictability into the backline with his kicking and give more support to flyhalf Bernard Foley, who has up to now been the Wallabies' key point of attack along with fullback Israel Folau.
Israel Folau, 14 Dane Haylett-Petty, 13 Tevita Kuridrani, 12 Matt
Toomua, 11 Rob Horne, 10 Bernard Foley, 9 Nick Phipps, 8 Sean McMahon, 7
Michael Hooper, 6 Scott Fardy, 5 Rob Simmons, 4 Will Skelton, 3 Sekope
Kepu, 2 Stephen Moore (captain), 1 James Slipper
player to be left out): Tatafu Polota-Nau, Scott Sio, Greg Holmes, Adam
Coleman, Dean Mumm, Wycliff Palu, Nick Frisby, Christian Leali’ifano,
Mike Brown, 14 Anthony Watson, 13 Jonathan Joseph, 12 Owen Farrell, 11
Jack Nowell, 10 George Ford, 9 Ben Youngs, 8 Billy Vunipola, 7 Teimana
Harrison, 6 Chris Robshaw, 5 George Kruis, 4 Maro Itoje, 3 Dan Cole, 2
Dylan Hartley (captain), 1 Mako VunipolaSubstitutes: 16 Jamie
George, 17 Matt Mullan, 18 Paul Hill, 19 Joe Launchbury, 20 Courtney
Lawes, 21 Jack Clifford, 22 Danny Care, 23 Elliot Daly