HONG KONG: World number one Angelique Kerber crashed out of the Hong Kong Open in the quarter-finals on Friday, the German slumping to a shock 6-3 6-1 defeat to Australia's Daria Gavrilova at Victoria Park.

Kerber, who also suffered a surprise loss to Elina Svitolina in the round of 16 at last week's China Open, committed six double faults and struggled on serve as her 38th-ranked opponent secured victory in an hour and 14 minutes.

Moscow-born Gavrilova fired five aces against the German as the 22-year-old continues her quest for a first WTA singles title, and she will next face Frenchwoman Kristina Mladenovic for a place in the final.

Her victory over Kerber, who surged to the top of the rankings after winning the Australian and U.S. Open titles this year as well as reaching the Wimbledon final, was her first against the German Olympic silver medallist in six meetings.

Mladenovic defeated American Bethanie Mattek-Sands 3-6 6-3 7-6(3) in the second quarter-final. Jelena Jankovic is the defending champion and the Serb faces another Frenchwoman, Alize Cornet, in a last eight encounter later on Friday.