LONDON (Reuters) - Serena Williams hit top gear in deposing champion Petra Kvitova and ominously for her Wimbledon semi-final opponent Victoria Azarenka the four-times champion says she has nothing to lose in the last-four clash on Thursday.

Williams, who banged down 13 aces in her quarter-final rout of Kvitova, faces the Australian Open champion and world number two in what is likely to be a decibel-busting clash between two of the game's great grunters.

"It's going to be another match where I have absolutely nothing to lose," sixth seed Williams said after blitzing Kvitova. "I can just go out there and enjoy myself and have fun."

The Belarusian, who beat Tamira Paszek to book her place in the semi-finals, has only beaten Williams once in eight meetings.

"She's a great fighter," Azarenka said. "She never gives up. You always see that, no matter what the score is, she will go for her shots...

"I don't really like to look back in history because every time you step on the court it's a new story. You kind of write your own history every time."

In the other semi-final, world number three Agnieszka Radwanska takes on eighth-seeded German Angelique Kerber.

"I think against Radwanska it will also be a long match and a tough one because she moves very well on grass," Kerber said.

(Reporting by Toby Davis; editing by Ed Osmond)