The actual trophy is irrelevant - it's the bragging rights associated with it that are most at stake. Last weekend against the Springboks, the All Blacks paid the price for having a month's R&R, and also for being overtly cock after their Lions whitewash.
Their coach Graham Henry should have known better than to send an "underdone" team out to face one of the most physical sides in the world, especially away from home. The Springboks fully deserved their win, but they will find it hard to get wins in both Australia and New Zealand in the coming weeks.
The away bonus point garnered by the All Blacks in last weekend's 22-16 loss to the 'Boks could yet prove crucial in the final Tri-Nations shake up - as it did last year when the South Africans managed to gain two bonus point-losses away from home.
While the All Blacks dominated possession and territory in Cape Town, they failed to take their chances, especially those created by lively winger Rico Gear. The "in your face" Springboks defence was simply magnificent and a complete contrast to the flimsy type of tackling offered by the touring Lions. New Zealand did look the more adventurous side and will look to bounce back against the Wallabies on Saturday.
The All Blacks have only won three times from 14 visits to Sydney in recent years, but the Australians look in disarray. Their "unruly" antics on tour, combined with two back-to-back losses to South Africa, has led to the circling of wagons within the Wallaby camp.
Some ex-Wallaby players have been calling for the heads of captain George Gregan and coach Eddie Jones - they both know there's no worse nation in the world to be in when you are losing than Australia.
The Wallabies are under huge pressure to win against their old foe this weekend, and their cause has not been helped by a host of injuries to key players, not least to their talismanic out-half Stephen Larkam. Matt Giteau is in at number 10, and the Australian back line welcomes two full Test match debutants in ACT Brumbies winger Mark Gerrard, and Queensland's young Super 12 full-back Drew Mitchell.
If you look at the backs that Australia are missing for this match, such as Wendell Sailor, Matt Rodgers, Chris Latham and Larkam, then they will certainly boast a formidable line-up whenever they are restored to strength.
The Wallaby coaches obviously watched the Springbok pack's performance from last week, and have elected to go with a big powerful back row. David Lyons returns at number 8 after a recent lay-off with illness, and the 17-stone John Roe is preferred to the diminutive Phil Waugh on the blindside of the scrum - presumably to add some meat to the Aussie defensive screen. This would indicate the Wallabies are going to try and boss the All Black loose forwards at second phase play, much in the same way the Springboks did.
The All Blacks, in contrast, will still try to play the ball wide, especially with two new caps in the Australian back three. All Black flanker Richie McCaw needs to be more involved than he was last week, especially if the running game is going to remain the All Blacks' priority. It is good to see the return of Joe Rokocoko to the wing, allowing last week's ineffectual winger Mils Muliania back to his preferred position of full-back. The heat is on the Fijian-born Rokocoko to perform, as he has been sadly out of form during the last year.
Biases aside, the All Blacks are in better shape than Australia, with only Byron Kelleher (concussion) out through injury. Skipper Tana Umaga has shaken off his ankle injury to start. Kelleher's replacement at scrum-half, Piri Weepu must get the All Black back line moving, as well as taking some of the heat off targeted number 10 Dan Carter.
Last weekend Weepu's passing allowed the 'Bok backrow to shut Carter off at source, and Weepu is certainly not in the same league as either Justin Marshall, Byron Kelleher or for that matter, George Gregan.
The pressure is all on the Aussies, another loss and they are out of the Tri-Nations already, and with some of their big names under-performing, the axe will fall.
The All Blacks must show that they are more than just a one-dimensional team - that they have a "Plan B" in their arsenal. Against the Lions, the "Blacks had no need to move into second gear, but on Saturday, they will need to mix some fight with flair. I have to say, given the present state of the Australian game, the All Blacks should prevail.