- New Zealand plays Australia in World Cup final
- All Blacks defending title from 2011
- Wallabies have also won tournament twice
(CNN)This is the moment rugby fans have been anticipating for four years.
After 47 matches played by 20 nations in the past six weeks, attended by over 2.3 million people, the 2015 Rugby World Cup will be down to just two teams on Saturday -- one of which is guaranteed to make sporting history by winning the final at Twickenham.
Can New Zealand's All Blacks become the first side to retain the title? Or will Australia's Wallabies win the race to become the first country to be crowned champion on three occasions?
CNN Sport talks to past winners of the tournament and breaks down the key clashes ahead of the Down Under showdown at the home of English rugby.
Brad Thorn, former All Blacks forward
"Our job as an All Black is to win. That's it. Win. Don't try hard and lose. Win -- that's the pass mark," says the 40-year-old, who represented Australia in rugby league before switching codes and helping his native New Zealand end a 24-year wait for World Cup success on home soil in 2011.
"If they get this job done, back-to-back World Cups, the first time it's ever been done, they'll have the most World Cups -- three, South Africa and Australia have two each -- and they'll be considered one of the greatest teams of all time."
George Gregan, former Australia captain
"It'll go right down to the wire," says Gregan, who was a member of the Wallabies team that won the 1999 World Cup, and was skipper in the 2003 final defeat against England.
"They've played twice this year and won one each -- the Wallabies beat the All Blacks in Sydney and the All Blacks thumped the Wallabies a week later at Eden Park, but it was a different team," he adds.
"Does that mean anything? No, all it means is they know each other's game and what's required against each other, and it comes down to the best performer on the day."
Lawrence Dallaglio, former England captain
"You've got to remember that New Zealand has only lost three matches in the last 53 under Steve Hansen, so that's a pretty impressive record," says the 43-year-old, who played in every match of his country's 2003 winning campaign in Australia. referring to the All Blacks head coach.
"But one of the teams that's beaten them has been Australia, and the only team to beat them this year. That's what makes this match very exciting.
"On balance, NZ are favorites, you have to say, but there's always that little bit of doubt because Australia are one of the few teams in the world that have the belief and the ability to win."
John Smit, former South Africa captain
"It's deservedly between the best two sides of the last 12 months. It's quite cool that the two best teams who have shown the best form are meeting each other in the final," says Smit, who led the Springboks to their second title in 2007.
"It's a disappointment for the South African point of view, and everyone else's point of view, but we've seen two really good sides playing really good rugby, now playing in the World Cup final, which is going to be great for the tournament as a whole."
Alex Thomas, CNN World Sport presenter
"New Zealand will start the final as favorites and are sure to have taken notice of the fact that Australia conceded eight penalties in their own half against Argentina (in the semifinal) -- four of them were under pressure from the Pumas' superior scrummaging. That could be something the All Blacks look to exploit," says Thomas.
"While Adam Ashley-Cooper's hat-trick of tries against Argentina grabbed the headlines, it was the return from injury of back-row forward David Pocock that was the key to the Wallabies' success. His four turnovers was more than double anyone else on the pitch and he also made 14 tackles, the third best in the game.
"Australia is the only team to have a winning record against the All Blacks at the World Cup and is perhaps the only team not phased by their fearsome reputation."
The national rivalry
New Zealand is Australia's smaller neighbor both geographically and in terms of sporting resources, but in rugby terms it has held the ascendancy in recent years -- the Wallabies' two World Cup successes were in the 1990s.
Their rugby rivalry is intense, but has never reached the levels of bitter acrimony that followed the infamous "underarm bowling" incident instigated by Australian cricket captain Greg Chappell against the Kiwis in 1981.
There had been some talk of upping the ante for the final by also putting the Bledisloe Cup at stake. The trophy, contested by the two teams since 1932, has been held by New Zealand for 12 years -- and for some, keeping it means as much as lifting the Webb Ellis Cup.
New Zealand's 2011-winning skipper Richie McCaw has postponed any announcement about his future until after the tournament, but this is expected to be the inspirational 34-year-old's final, record-extending 148th international appearance. He will match Jason Leonard's record of 22 World Cup caps.
The flanker's battle at the breakdown with Aussie rivals Pocock and Michael Hooper will have a big influence on the final outcome.
Born in Saudi Arabia, with Irish parents, Stephen Moore is the first hooker to captain Australia since 1995.
His role in the front row of the scrum has been key in the transformation of the once-derided Wallabies pack under the guidance of former Argentina star Mario Ledesma, who also wore the No. 2 jersey.
The No. 10s
Fly-half is a pivotal position in rugby, providing the lynchpin for teams' attacking decisions -- and it can be argued there are none greater than New Zealand's Dan Carter, and none more injury prone.
This is the last hurrah for international rugby's leading points scorer, who was ruled out during the group stages in 2011 and had to watch his teammates lift the Webb Ellis Cup from the sidelines, on crutches.
While his long list of injuries have taken their toll, the 33-year-old is still one of the best. He kicked a vital -- and unexpected -- drop-goal in the 20-18 semifinal win over South Africa, swinging the momentum when his side was reduced to 14 men.
Australia's Bernard Foley had a relatively off-day in the 35-34 quarterfinal win over Scotland but still kept his nerve to kick a controversial decisive late penalty -- one of 15 he has landed during the tournament, the fourth highest.
He kicked the match-winning penalty in the 2014 Super Rugby final for the Waratahs, showing his cool on the big occasions, and he could play a key role if the All Blacks concede as many penalties as they did against the Springboks.
New Zealand's Julian Savea has scored a record-equaling eight tries so far in this tournament, matching compatriot Jonah Lomu (1999) and South Africa's Bryan Habana (2007).
Nicknamed "The Bus," he crossed for a hat-trick in the 62-13 demolition of France -- so often the All Blacks' bogey team -- in the quarterfinals.
On the opposite wing, relative newcomer Nehe Milner-Skudder has proved a potent complement to Savea's power. Four of his five tries came in the group stage, against Namibia and Tonga, but his tricky running tested both France and the tough-tackling Boks.
Australia has plenty of fire-power in Drew Mitchell, who is just one try short of Lomu and Habana's overall record of 15 -- though the South African can move into the outright lead by scoring in Friday's third-place playoff agaimnst Argentina.
Both Mitchell and Ashley-Cooper have both contributed four scores from the wings this tournament, but will face a defense that has given up only four tries in six games.
Hansen started his international coaching career with Wales, but returned to New Zealand and served as assistant to Graham Henry during the disastrous 2007 campaign and the 2011 success that brought such relief to Kiwi rugby fans.
He took over the mantle and has continued Henry's philosophy of developing a seamless team culture based on togetherness, strength in depth and perfecting simple routines. The results speak for themselves -- the man known as "Shag" has a winning ratio of 90.5%, losing just three times in 53 games and drawing twice, and been named world coach of the year the past three seasons.
Hansen's counterpart Michael Cheika has made a remarkable impact on Australia's fortunes since taking over from Ewen McKenzie in late 2014.
After a rocky start to his tenure on that year's northern hemisphere tour, the former Waratahs, Leinster and Stade Francais coach has given the Wallabies a more resilient backbone, in large part due to his decision to bring in Ledesma.
Australia won the truncated pre-World Cup Rugby Championship, beating New Zealand, Argentina and South Africa, then sealed England's early exit in this tournament.
Nigel Owens' appointment for the final made headlines due to the Welshman being one of the few openly-gay men in top-level rugby, with a backstory of depression and attempted suicide, but it was also a popular decision within the game.
Both teams will be happy with his philosophy of letting the game flow wherever possible.
"Nigel is clearly the best referee in the world," All Blacks selector (and 1987 World Cup winner) Grant Fox told a New Zealand radio station.
"But one of the key things he does, apart from communicating incredibly well with players, is that he lets the breakdown breathe. And that's really important. If you want to get a good contest and spectacle you've got to let the breakdown breathe a little bit, and he is really, really good at that. "
This is the first time the two teams have played each other in the final, but 2007 is the only World Cup when neither nation has been involved in the title match.
The Wallabies beat the All Blacks in the semifinals in 1991 and 2003, but lost their encounter at the same stage four years ago.
In this tournament, New Zealand has scored the most points (256) and most tries (36) of all teams in its six matches, but Australia has profited from more penalty kicks (15 to the All Blacks' 7) -- which could be vital in a tight match.
New Zealand has the advantage in clean breaks (61-46), carries over the gain line (325-253), lineout steals (14-8), most meters made (3,464-2,379), offloads (53-35) and turnovers (45-42) -- despite Pocock's leading tally of 14.
Australia leads the tournament tackle count, with 726 to the All Blacks' 551 -- this is a reflection of its more difficult route to the final, having topped the so-called "group of death" including host England and Wales.