Australia still hold a 13-point lead in the International Cricket Council's world test standings, but their grip on the No. 1-ranking appears to be loosening following a 2-0 series defeat to India on Monday.
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The loss, which India achieved through better execution of their all around skills in the conditions, was Australia's heaviest since going down 3-1 to the West Indies in 1988-89.
Ricky Ponting's winning percentage as captain now stands at 68.75 and has fallen below the mark of Steve Waugh (71.92), his world-beating predecessor.
Australia will start next week's two-test series against New Zealand under pressure and their ranking, officially and unofficially, will also be challenged with a home-and-away series against South Africa over the next five months.
The way Ponting's team performed during the four tests here also gave England hope of reclaiming the Ashes in 2009.
Former captain Ian Botham said last week that England would win easily because of Australia's seemingly weak bowling attack, which is still rebuilding after losing long-standing spearheads Glenn McGrath and Shane Warne.
"I'm not pointing the finger at anyone or any aspect," Ponting said of the loss.
"At certain times our bowling's been off, at different times our batting's been off as well.
"India have been better than us in every aspect of the game."
India, who moved to second place in the test rankings, are riding a wave of success under new captain Mahendra Singh Dhoni.
They will face England in a seven-match limited-overs series starting next week, followed by two tests in December.
Dhoni, who led India to the Twenty20 World Cup title last year, stepped into the leadership role for two tests this series, first when former captain Anil Kumble had a right shoulder injury at Mohali, and then when Kumble retired on the final day of the drawn third match.
Both times when Dhoni was in charge, India won convincingly.
The hosts earned a 1-0 lead after beating the Australians by 320 runs at Mohali, a win set up by the excellent reverse-swing bowling of Ishant Sharma and Zaheer Khan, then Dhoni guided the side to a 172-run victory in Nagpur in the fourth test that ended Monday.
The win meant India regained the Border-Gavaskar trophy it lost here in 2004.
Pacers on form
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"I must say that the pacers did the trick, not only in this match, but in the series," Dhoni said.
"On these tracks, it was not easy because there was not much in the wicket, but they still bowled their heart out.
"It's not only the new ball, they bowled well with the old ball as well.
"Even when the ball was 60-overs old, they were giving their best."
Man-of-the-series Sharma picked up 15 wickets at an average of 27.06, becoming the first Indian fast bowler since Kapil Dev in the 1980s to win such an award for a home series.
His dominance of Ponting, whom he dismissed three times, and Khan's three
consecutive dismissals of opener Matthew Hayden, meant the visiting batsmen could not assert themselves as usual.
India's pacemen were able to swing the ball throughout the series in both the traditional and reverse methods.
Australia's quicks, none of which had played a test in India before, were slow to catch on and were unable to get on top of India's batsmen.
Opener Gautam Gambhir hit a series-high 463 runs at an average of 77.16 before missing the final test due to suspension, while Sachin Tendulkar, Virender Sehwag and VVS Laxman also passed the 350-run mark.
Michael Hussey was the only Australia to score as heavily.
Once the fast bowlers had caused early damage, the spinners then turned the heat on Australia.
Harbhajan Singh matched Sharma's 15 wickets and Amit Mishra, playing in his first series, looked a capable replacement for Kumble, taking 13.
When Australian offspinner Jason Krejza made his debut in the final test at Nagpur, he grabbed 12 wickets, one less than Australia's series-leader Mitchell Johnson, who was inconsistent at times across the four tests and potent at others.
Like Australia, India now starts a rebuilding phase following the exits of former captains Kumble and Sourav Ganguly, who retired after the fourth test.
Rahul Dravid and Tendulkar are also at the latter stages of their careers, but Ganguly said the series win was an important boost.
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"We've competed with Australia very well," Ganguly said.
"It definitely holds good for the future, but at the same time it just shows that the seniors are still good enough.
"My time is up but people like Sachin, Rahul and Laxman are still fantastic."
The teams have completed two animated test series in less than a year and are not due to meet again until a one-day contest at India in October 2009.
The acrimony between the sides was not as intense as in Australia in 2007-08, which peaked with a race row between Harbhajan and allrounder Andrew Symonds, but there were regular explosions.
Gambhir was banned for one match after elbowing Australian bowler Shane Watson in the chest during the third test, then lost his appeal.
Watson was fined 10 percent of his match fee for his verbal provocation which led to Gambhir's physical action.
At Mohali, Khan was docked 80 percent of his match payment for his over-the-top celebration of Hayden's second innings dismissal.
Ponting also was fined 20 percent of his match fee for poor over-rates in the final test, while his teammates were docked 10 percent.
During India's second innings in Nagpur, Ponting was so concerned about the possibility of suspension that he used part-time spinners to lift the rate in a move which contributed to Australia handing back the ascendancy in the match and the trophy.
"This tour we've just been totally outplayed," Ponting said.
"With the exception of the first test where we pretty much dominated that game, in any other game we've got back to level, but never really got in front."