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The Russian won her first grand slam title at Wimbledon eight years ago, before going on to win the US Open in 2006 and then then Australian Open four years ago.
CNN: Sharapova overpowers Errani to win French Open
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Of the overseas challengers, Australian Geoff Ogilvy has used his 2006 US Open victory as a springboard and is a realistic contender after reaching fourth in the world with two wins so far this year.
BBC: Woods ready for Masters campaign
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Woods has twice come into a major after a long lay-off, with mixed results - he missed the cut in the 2006 US Open at Winged Foot after his father died, and he won the 2008 US Open at Torrey Pines while playing on a seriously injured left knee.
BBC: Tiger Woods to return to golf at the Masters