Russia's Maria Sharapova will regain the world number one ranking after Amelie Mauresmo and Svetlana Kuznetsova suffered surprise defeats in the Australian Open fourth round yesterday.

After current top-spot holder Justine Henin-Hardenne withdrew from the Melbourne Park event for personal reasons, Sharapova ensured there would be a new No. 1 by reaching the last 16 at the year's first grand slam.

Sharapova and Frenchwoman Mauresmo were set to vie for the elite ranking but with the defending champion's defeat in Melbourne and the Russian having fewer points to defend, most of the permutations were made redundant.

Only third seed Kuznetsova could have deprived her fellow Russian of top spot if she had won the tournament and US Open champion Sharapova lost her fourth-round match to Vera Zvonareva on Monday.

That equation was also scratched on Sunday after Kuznetsova fell to Israel's Shahar Peer.

Mauresmo has spent 39 weeks as the world number one in her career, while Sharapova, who last topped the rankings in August 2005, has enjoyed the honour for seven weeks.

Kim Clijsters, Martina Hingis and Serena Williams are the only other remaining women at the Melbourne Park event to have held the top ranking.