The post-Ponting puzzle
The next two days might not deliver a victory for Australia, but they should provide some clarity on the team's batting setup. Whatever happens in this match, Australia's batting order will change for their next Test against Sri Lanka in Hobart. It might be as simple as a straight swap with a middle-order batsman replacing the retiring Ricky Ponting at No. 4. Alternatively, the whole structure of the batting order might be altered in the post-Ponting era.
If the selectors decide Phillip Hughes is the man most deserving of a call-up, does he have to open? Would they install him at No. 3 and move Shane Watson down? Will this be the time that Michael Clarke decides to challenge himself at first drop? The events over the next two days, on a good WACA pitch with plenty of runs in it, will not provide these answers alone, but they will be contributing factors when John Inverarity and his selection panel discuss their options afterwards.
The opening partnership is one of the most interesting puzzles. Over the past two Tests, both Ed Cowan and David Warner have scored impressive hundreds. But rarely have they clicked together. When they walked out onto the WACA to begin this enormous chase of 632, it was their 17th Test opening partnership. Only once - in Perth last summer - have they posted a century stand. Justin Langer and Matthew Hayden, the gold standard by which all new Australian opening combinations will be judged, managed six century stands in their first 17 innings.
Cowan and Warner began solidly on this occasion. They went to stumps at 0 for 40 and have the opportunity to make their case for permanent residency at the top of the order on Monday. At their best, they are an odd couple whose differences - Warner is aggressive while Cowan is watchful - can be complementary, but at their worst they contribute too often to Australia's shaky starts. Since they have been opening, Australia have been three down for less than a hundred more often than not.
Part of that also comes down to the No. 3 position. The challenges of the post-Ponting era can be glimpsed by the way the Australians have struggled to find a first-drop since Ponting moved to No. 4. In that time, the only century an Australian No. 3 has scored is by Shaun Marsh, on debut in Sri Lanka - the innings that encouraged the Australians to shunt Ponting down in the first place. Marsh faltered, Usman Khawaja didn't grasp his opportunities, Rob Quiney failed and Watson has teased without delivering.
In his seven innings at first drop, Watson has made 39, 52, 56, 0, 41, 5 and 10. At his best he can destroy a new-ball attack, but he is vulnerable to lbws and to the lack of rest that his top-order position allows him after he has bowled. He has a chance in this innings to score the kind of century that Australia need from their No. 3. Otherwise, he might find himself slipping further down the order to accommodate Ponting's replacement.
Of course, there is the possibility of Clarke, the highest-ranked Test batsman in the world, moving himself up to first drop. But does it make sense to alter the part of Australia's batting line-up that is working best, the middle order, to patch a hole at the top? Would he have the same impact against the new ball as he has coming in at three down? Even if those three wickets have fallen cheaply, the shine has generally been taken off by the time he has come in.
If the line-up fizzles again on Monday, Clarke might find himself forced to consider the possibility more seriously for the upcoming Sri Lanka series. Michael Hussey, in form for the time being, appears unlikely to move from No. 6. And Ponting is departing regardless of what happens in Perth.
Much will depend on who the selectors choose to replace him - Hughes, Khawaja, Quiney, Alex Doolan or a bolter - and where that person is used to batting. But Australia's batting over the next two days will also be a factor. Australia's chances of victory are as slim as Bruce Reid, but the batsmen still have plenty to play for.
Brydon Coverdale is an assistant editor at ESPNcricinfo. He tweets here