Sharapova progresses in Miami

Maria Sharapova moved a step closer to a fourth consecutive final appearance at the Sony Open as she overcame Petra Kvitova in straight sets in Miami.

The Russian - who has never won at Crandon Park but has made the final five times, including the last three years - eased through to the semis with a 7-5 6-1 win over her fellow former Wimbledon champion.

Sharapova broke her Czech opponent seven times en route to victory with Kvitova winning just 28 per cent of points on her second serve.

In the men's event, second seed Novak Djokovic made relatively untroubled progress to the quarter-finals as he overcame Spain's Tommy Robredo 6-3 7-5.

"(It was a) very solid win," the Serbian told www.atpworldtour.com. "I made him play an extra shot in important moments and that's why I'm satisfied with the overall match today."

Djokovic will face Andy Murray in the next round after the defending champion claimed a convincing straight sets victory over Jo-Wilfried Tsonga.

Another two-time champion eased into the next round as Roger Federer earned a straightforward 6-4 6-1 win over Richard Gasquet.

Australian Open champion Stanislas Wawrinka suffered a shock exit, going down in three sets to Alexandr Dolgopolov.

The first two sets were tight affairs but the Ukrainian found his rhythm in the third and eased to a 6-4 3-6 6-1 victory.

Fourth seed David Ferrer suffered a surprise exit as he lost a gruelling contest against Japan's Kei Nishikori.

The world number 21 took the first set on a tie-break but Ferrer came storming back to win the second before Nishikori claimed a second tie-break to close out a 7-6 (9/7) 2-6 7-6 (11/9) victory.