A win 'morrow will put the Indians 10 points clear of Lanka, which would then need to claim bonus-point victories in its final two matches to stake a final spot claim.
The two sides have split their two completed one-dayers in this summer, which followed a fiercely contested Test series.
India has delivered the goods with the bat against Sri Lanka but been unable to get on top of the Australian attack.
It bodes well for the future of Indian cricket that the team's batsmen have still been able to compile decent totals, albeit against Sri Lanka, despite Sachin Tendulkar, who has averaged 21, not featuring amongst the runs.
It has two of the tournament's leading four run-scorers in Gautam Gambhir and Mahendra Dhoni, the latter showing he is more than just a vicious strokemaker but also capable of occupying the crease should his team be in trouble.
He crashed an unbeaten 88 in Brisbane and also offered priceless hands in Melbourne and Adelaide when his team was under extreme pressure.
Yuvraj Singh's horror tour finally had a turn for the better in India's win last Tuesday in Adelaide, hitting 76 at better than a run a ball, and if Tendulkar can strike back the tourists' batting looks more than capable of defying the Australian attack.
Australia's top order has been its Achilles heel. Ponting, Matthew Hayden and Andrew Symonds have all failed to pass 50 in six matches. The trio have just 213 runs between them at a combined average of less than 14.
Unless another belter is produced in Sydney, like the wicket which produced 640 runs for a Ford Ranger Cup match last Wednesday, batsmen will again have to scrounge for their runs.
And staring them straight in the eye will be teenage sensation Ishant Sharma. He, along with a re-born Irfan Pathan, has clearly got the wood over the Australian line-up.
The Australian top order has too much class and ability to continue its run of outs but it will need quickly reverse its form if the home side is to defeat India on Sunday.
"I said this the other day, if we do hit our straps for the finals we're going to be very hard to beat. That's what we're all hoping we're going to do."
"We're going to keep working hard and try and get ourselves in the best condition that we can, physically and mentally and technically, for the remaining games."
Mitchell Johnson, in his first full summer of international cricket, will sit out Sunday's match but taking his place is pace spearhead Brett Lee, who has missed Australia's past two matches to freshen up.