This is quite the irresistible force against the immovable object, a potential humdinger if there was one. Australia, a potent mix of flair and substance, style and method, against Pakistan, effervescent and explosive, emotional and prone to wild mood swings. This has all the trappings of a classic; whether it does unspool into one depends on which Pakistan turns up at the Adelaide Oval on Friday (March 20).

On the face of it, the 'which Pakistan' reference might appear unfair and unjustified. After all, Misbah-ul-Haq's men have strung together four wins on the bounce after beginning the tournament with successive losses to India and West Indies. With elimination staring them in the face, they have managed to rouse themselves from a state of stupor, playing the brand of cricket which makes for such compelling viewing when they get it all together. The batting has been steadily efficient rather than spectacularly outrageous, and the bowling has been aggressive and relentless, pacy and probing.

And yet, with Pakistan, you always wonder. Their unpredictability demands attention. You can't take your eye off the action because every second is entertainment guaranteed, there are no boring or meandering passages of play.

Pakistan know they will have to be totally switched on, come Friday. No histrionics, no playing to the packed gallery, no playing for individual glory. They are up against a fearsome unit, a beautifully oiled machine with each part functioning at optimum efficiency. Australia are a team with seemingly no chinks, but if anyone can unearth and then hammer away at those chinks, it has to be Misbah's side.

Almost by accident and with great reluctance, Pakistan have hit upon a functioning opening pair. The continued overlooking of Sarfraz Ahmed despite Nasir Jamshed's poor form had to end at some stage. It did in the penultimate league game against South Africa, a match Pakistan had to win to stay in the hunt for a quarterfinal place. Sarfraz made 49, Pakistan won the rain-interrupted fixture by 29 runs. In the next game against Ireland, a virtual pre-quarterfinal, Sarfraz made a hundred. Where was he all this while?

Sarfraz and Ahmed Shehzad hold the key to Pakistan's fortunes as much as Wahab Riaz, Rahat Ali and Sohail Khan do with the ball. Australia are a side that love nothing more than getting stuck into the opposition early, and then feeding off the momentum. Michael Clarke's team are past masters at doing the front-running, and with Mitchell Starc in such stunning form, they fancy themselves to make early inroads every single time. Sarfraz and Shehzad will have to recalibrate their approach to the new ball if they are to set the platform from which Misbah, Umar Akmal and Sohaib Maqsood can dictate terms.

There is a lightness to the Pakistani batting that wouldn't have escaped Australia's keen eye. Younis Khan's continued poor run means it will be a gamble to field him in a match with so much riding on the result. Does Misbah go for his former captain's experience and hope that it is put to good use in a big match? Or does he pin his faith in a younger man, say Haris Sohail, who is unfettered by failure and who can also offer handy overs of left-arm spin?

Pakistan have played twice before in Adelaide in this World Cup, and have been in the South Australian capital for nearly 10 days now. Even though they are up against the host nation, they will not be short of support from either their travelling fans or from the expats who have now made Australia their home. They know the surface as well as any other team, but then again, so do Australia, of course.

Australia have had just one poor half-game - when they were blown away by Trent Boult for 151 in Auckland - and even then, they only lost by one wicket. Otherwise, they have been impressive, intimidating even. Their conquests of England in the opening game and of Sri Lanka in a high-scoring contest in Sydney are suggestive of a team that is not only powerful, but that also knows that it is powerful. There is power in the batting from one to eight, there is power in the bowling. Starc has been the leading light with 16 sticks, but Australia are far from a one-man army. Mitchell Johnson is always a lurking danger, capable of exploding without warning. James Faulkner's availability adds a whole new dimension, especially at the death where his changes of pace make him almost impossible to put away. Australia have alternated between Josh Hazlewood and the quicker Pat Cummins as the right-arm option; whoever gets a look-in on the morrow will look to prove a point.

Australia have by and large been a pace-oriented attack, Xavier Doherty's left-arm spin summoned only for the clash against Sri Lanka in the belief that the SCG surface might assist the spinners. It's almost a given that Doherty will sit on the bench for this game too, with Glenn Maxwell donning the spinning shoes. Too many pacers might suggest a one-dimensional mode of attack, but each of Australia's quicks, left or right, brings a different skill, a different dimension.

Matches against Afghanistan and Scotland, in particular, allowed Australia to give all their top-order batsmen decent game time before the quarterfinals. The biggest gains in the last few days have been Clarke's occupation of the crease, and Shane Watson rediscovering the runs on the SCG belter against Sri Lanka. At 5 or 6, Watson provides great muscle to the batting; at 3, Steven Smith provides steel and stability. It's an awe-inspiring line-up with Brad Haddin at No. 8. For all their bowling wealth, Pakistan will rest a little uneasy.

And, make no mistake, Pakistan have a plethora of bowling riches, even though Mohammad Irfan has been ruled out of the rest of the competition with a pelvis injury. Wahab has been the enforcer with Rahat and Sohail playing able foils; Shahid Afridi hasn't hit wicket-taking mode but has been his usual pressure-building self, allowing the quicks to feed off his parsimony. If Misbah can work his combination around to bring back Yasir Shah, the legspinner, it will make the attack more menacing but might end up weakening the batting. A tricky call, that.

As Sri Lanka bowed out of the World Cup on Wednesday, ODI cricket bid goodbye to Kumar Sangakkara and Mahela Jayawardene. Misbah and Shahid Afridi, not for the first time, have also said they intend retiring from ODI cricket at the end of the World Cup. It is unlikely that they, or the rest of the team, will settle for a quarterfinal exit. But for that, Australia must be felled. Even for mercurial, unpredictable Pakistan, that will be quite a challenge.

Teams (from):

Australia: David Warner, Aaron Finch, Steven Smith, Michael Clarke (capt), Shane Watson, Glenn Maxwell, James Faulkner, Brad Haddin (wk), Mitchell Starc, Pat Cummins, Mitchell Johnson, Josh Hazlewood, George Bailey, Mitchell Marsh, Xavier Doherty.

Pakistan: Sarfraz Ahmed (wk), Ahmed Shehzad, Haris Sohail, Misbah-ul-Haq (capt), Umar Akmal, Sohaib Maqsood, Shahid Afridi, Wahab Riaz, Rahat Ali, Sohail Khan, Ehsan Adil, Younis Khan, Yasir Shah, Nasir Jamshed.