Rafa Nadal returns to action at the Australian Open on Thursday, with American qualifier Ryan Sweeting handed the Herculean task of ending the Mallorcan's march toward a fourth consecutive grand slam title in the second round.

Sweeting, a Bahamas-born 23-year-old with a world ranking of 116, has yet to earn an ATP title and will do well not to resemble cannon fodder at Rod Laver Arena in his first match against the nine-times grand slam champion.

Nadal's first-round opponent Marcos Daniel retired injured when trailing 6-0 5-0, and the Spaniard might hope for a more solid work-out as he strives to become the first man since Rod Laver in 1969 to hold all four grand slams concurrently.

Last year's runner-up Andy Murray also benefited from an early retirement but had all but beaten Karol Beck before the Slovakian pulled the plug with a shoulder injury.

Murray, who wept bitter tears when beaten in straight sets by holder Roger Federer last year, will play 79th-ranked Ukrainian Illya Marchenko on Margaret Court Arena as he seeks to end Britain's long wait for a grand slam champion.

Former U.S. Open champion Juan Martin del Potro continues his cautious return to grand slam action against former finalist Marcos Baghdatis of Cyprus.

U.S. Open champion Kim Clijsters plays the early match at Rod Laver Arena against Carla Suarez Navarro and should be too strong for the 62nd-ranked Spaniard.

Russian world number two Vera Zvonareva's bid for a maiden grand slam continues against Serbia's Bojana Jovanovski.

Sam Stosur, who holds Australia's greatest hope of ending a 33-year wait for a home grand slam champion, will play Russia's Vera Dushevina in the evening session at Rod Laver Arena.

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