Serena ousts Maria

Novak Djokovic hammered an off-key Kei Nishikori and Roger Federer put on a masterclass against Tomas Berdych as they set up a dream semifinal at the Australian Open on Tuesday.

Defending champion Djokovic recovered strongly from his five-set struggle against Gilles Simon as he ousted Nishikori 6-3, 6-2, 6-4, after Federer swept aside Berdych 7-6 (7/4), 6-2, 6-4.

Djokovic is seeking his 11th Grand Slam title while Federer, 34, is looking to extend his record tally to 18 -- and both will want to take charge of their head-to-head, which is locked at 22-22.

Meanwhile, Serena Williams beat Maria Sharapova for an 18th straight time to set up an Australian Open semifinal against Agnieszka Radwanska.

The six-time Melbourne Park champion heaped more misery on her long-time rival 6-4, 6-1, with the Russian fifth seed stretching her demoralising winless run against the American great to 12 years.

The signs are not good for Radwanska, despite her convincing 6-1, 6-3 win over Spanish 10th seed Carla Suarez on Rod Laver Arena. While her record against Williams is not yet on the scale of Sharapova, it is still dismal.