SERENA WILLIAMS cannot wait for her grudge semi-final with Maria Sharapova, claiming: "I think she brings out the best in me".

Top seed Williams outslugged close friend Victoria Azarenka in a three-set thriller to set up a last-four battle with Russia's 2004 Wimbledon champion Sharapova.

Reigning Australian and French Open champion Williams moves ever closer to a career-first calendar grand slam as she struts through Wimbledon, admitting she will relish facing Sharapova – a foe she has beaten in 16 consecutive meetings.

Two years ago Williams appeared to brand Grigor Dimitrov "the guy with the black heart" after their relationship broke down. Now the Bulgarian dates Wimbledon's fourth seed Sharapova, and that axis keeps the relationship between the American and the Russian terse at best.

"I love playing Maria, I think she brings out the best in me," said 20-time grand slam champion Williams. I think I bring out the best in her.

"I don't feel I have any pressure going into this match. We both are enjoying this moment and one of us will be in the final."

Williams bludgeoned past the resurgent Azarenka in an engaging contest, serving 24 aces to dislodge the former world No.1, who is finding form after two years' injury woe.

The 33-year-old shrugged off Azarenka's big-hitting prowess to prevail 3-6, 6-2, 6-3, admitting taking on her Belarusian friend always offers her a barometer of form.

Any potential opponent taking a reading from this contest will have struggled not to heed the omens: Williams is surely now the overwhelming favourite to claim the third leg of that calendar slam at SW19.

Sharapova was dragged into a three-set battle of her own by America's Coco Vandeweghe, but came through 6-3, 6-7 (3/7), 6-2, to book that Williams clash.

Agnieszka Radwanska beat Madison Keys in three sets to reach the semi-finals for the third time.

The 26-year-old Pole, finalist in 2012, used her craft and guile to overcome American Keys 7-6 (7-3), 3-6, 6-3.

Radwanska, the 13th seed, edged a tight first set and secured the decider with the only break after the heavy-hitting Keys, 20, responded.

"It couldn't be any better. I'm so happy," Radwanska said. "It was very tight, point by point, game by game. Serve was the key so one break and there you go."

Her last-four opponent will be Spain's 20th seed Garbine Muguruza, who beat Timea Bacsinszky 7-5, 6-3.