Fitness will decide the final of the Rugby World Cup.
Australian coach Eddie Jones says England are the best team in the world and if Australia are with them at 70 minutes on Saturday night fitness will be the difference.
Jones believes England have the ability to play with greater width but will opt for a much shorter, narrower game in the final.
"I think this week it will go down to the wire,” he said. “I'm sure at 70 minutes both teams are going to be in a position to win the game.
“They've changed their game considerably during the Tournament, they are just playing to their strengths.
Will there be width?
“They still have the ability to play with greater width but certainly they've playing a much shorter, narrower game in this World Cup than they've been playing previously.”
Injured Wallaby number 8 Toutai Kefu suggests this narrow approach is a result of an ageing forward pack, unwilling or unable to cover the kilometres needed to match the expected width of the Wallabies.
“Some of the England forwards looked a little red faced against Samoa,” Kefu told the Daily Telegraph this week.
“Samoa and Wales showed that England can be vulnerable to teams attacking them wide because it makes Dad’s Army move from side to side.
"The Pommy forwards love nothing better than keeping it tight so they don’t have to cover too many kilometres.”
Make it uncomfortable
Jones was not as forthright as Kefu but he did suggest Australia must make things uncomfortable for England if they are to win.
"What is crucial is fitness,” Jones said. “Fitness is definitely the key if the game is fast and the referee is to the edict of the Tournament, which is to have fast ball and get the tackler off the ball carrier, then fitness is going to be absolutely essential.
“Guys win Olympics at 36 years of age, you can still perform well in your mid-30s. It's not so much age, but it's going to be fitness and we'll certainly back ourselves on fitness."
Selection headaches
No matter the tactics or physical qualities needed to win on Saturday one of the hardest jobs Jones has had all Tournament has been at selection time, trying to fit 30 quality players in to 22 jerseys on game day.
"The positive thing about Australian rugby this year is that there has been such contention about selection,” he said.
“Which means we've got a number of good players who are missing out on the team. If you look at the guys who aren't in the 22.
They are all excellent players who have considerable futures in Australian rugby.
“To leave them out of the 22 is pretty healthy. There are seven blokes who've absolutely done everything they can to be as good as they can and they're not in the team.
“After every game, it's always the squad of 30 who has put together that performance. We've all trained hard, there's been a lot of 15 on 15 games in training.
"The quality of training has been very high and a lot of credit must go to the guys who are not in the side."
Harrison or Giffin
One such selection decision involves the continued use of lock Justin Harrison to start games ahead of vice captain and principle lineout caller David Giffin.
Giffin was injured in the Tournament opener and has slowly made his way back to the bench over the ensuing six weeks.
"At this stage, Justin will play the first part of the game the best,” Jones said. “Giff (David Giffin) has had an interrupted World Cup but we know he can come on in the second half and really give us a lot of experience.
"His performance last weekend was absolutely outstanding."
Different look
Australia have taken on a dramatically different look to the team beaten so comprehensively 25-14 in Melbourne on 21 June.
The only survivors are Bill Young in the front row, Nathan Sharpe at lock, backrowers David Lyons and Phil Waugh, captain George Gregan and wing Wendell Sailor.
"We've got a completely different side that played (England) in June,” Jones said. “We've got a young pack and they have no fear. They've got nothing to be frightened of.
“They'll play with a lot of aggression and if we're good enough we'll get on top of them and if we're not good enough, we won't. We've got no fear at all."
Jones said England have proven themselves to be the best side in the world.
“They're a very, very good side,” he said. “What we have to do is take them out of their comfort zone.
"We have to play the game how we want to play it, which is distinctly a different way from England, and if we do that, and individuals play well, then the team will play well."