Victory over rival Roger Federer at Melbourne Park, however, was his sole major triumph of a season blighted by injury.
The Spaniard has not won a title since May and became the first player to be knocked out of the ATP World Tour Finals in London with a second successive straight sets defeat.
Here we chart Nadal's slide in 2009.
Australian Open, January
The 22 year-old captured his sixth grand slam, and his first on hard courts, with a five-set victory over rival Roger Federer to become the first Spaniard to win at Melbourne Park. Nadal had beaten compatriot Fernando Verdasco in the semi-final in a marathon contest which lasted five hours and 14 minutes.
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Rotterdam, February
Injured right knee in three-set defeat to world No 4 Andy Murray at World Tour indoor final.
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Davis Cup, March
After missing Dubai Championships with injury, Nadal returned for first-round tie against Serbia and won both of his singles matches against Janko Tipsarevic and Novak Djokovic in straight sets.
Indian Wells Masters, March
Clinched 13th Masters title with crushing 6-1, 6-2 win over Murray for second time in three years in California.
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Miami Masters, April
Beaten in quarter-finals of Sony Ericsson Open by Argentina's Juan Martin del Potro after leading 3-0 in the third set before losing a tie-break.
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Monte Carlo Masters, April
Captures fifth straight title in Monte Carlo with 6-3, 2-6, 6-1 victory over third seed Novak Djokovic to extend winning streak to 27 matches at opening clay-court tournament of season.
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Barcelona Open, April
Powers to fifth consecutive Open title in Barcelona with 6-2, 7-5 win over Spanish compatriot David Ferrer.
Rome Masters, May
Posts straight-sets win over Djokovic for record fourth title in Italy and 15th Masters title.
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Madrid Masters, May
World No 1 sees 33-match winning run on clay brought to a halt in a one-sided 6-4, 6-4 loss to rival Federer in pair's 20th career meeting.
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French Open, May
Stunned by No 23-seeded Robin Soderling in the fourth round of Roland Garros. Fourth-set defeat ends 31-match winning streak in Paris.
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Queen's, Wimbledon, June
Withdraws from pre-Wimbledon event and third grand slam of the season, where he was defending champion in both, due to tendinitis in knees.
July
His 46-week reign as world No 1 comes to an end as Federer regains status at top of rankings with SW19 success.
Montreal Masters, August
Returns to action after nine-weeks on sidelines but suffers quarter-final defeat to Del Potro. He slips to third in rankings later in month for first time since July, 2005.
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Cincinnati Masters, August
In only second tournament back after two months off reaches semi-finals but loses in straight sets to Djokovic and picks up abdominal strain.
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US Open, September
Del Potro wrecks Nadal's title aspirations in Flushing Meadows with bludgeoning 6-2, 6-2, 6-2 in semi-finals but moves back up to No 2 in world rankings.
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China Open, October
Handed first defeat in Beijing by Croatia's Marin Cilic. Nadal, who won the 2005 Open title and gold at the 2008 Olympics, suffered 6-1, 6-3 defeat.
Shanghai Masters, October
Loses high-quality final to Nikolay Davydenko in straight sets.
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Paris Masters, November
Reaches semi-finals in French capital before losing to eventual champion Djokovic.
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World Tour Finals, November
Becomes first player to crash out of season-ending tournament in London after successive straight sets defeats to Robin Soderling and Davydenko.
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