Two-time Australian Open champion Naomi Osaka became the latest star to pull out of the opening Grand Slam of the year Sunday, leaving the tournament deprived of some of the biggest names in the game.

Former tennis world number one Ashleigh Barty has dashed hopes she will make a return to professional sport, after speculation the Australian could switch to golf.

Australia's Ash Barty has reclaimed the number one spot in the WTA rankings less than a month after losing it while U.S. Open champion Bianca Andreescu moved up to a career-high fifth after her maiden Grand Slam win in New York.