Madrid, Spain (SportsNetwork.com) - A pair of straight-set upsets took place in Friday's semifinals at the Madrid Open, as Petra Kvitova doused world No. 1 Serena Williams and Svetlana Kuznetsova knocked out defending champion Maria Sharapova on the red clay at The Magic Box.

The fourth-seeded Czech slugger Kvitova vanquished Williams 6-2, 6-3 to hand the powerful American her first loss since last year. Williams had been 24-0 this year and riding a 27-match overall winning streak before succumbing to the reigning Wimbledon champ and 2011 Madrid titlist Kvitova.

"I'm just exhausted today," said Williams, who had her serve broken six times. "But it's really good preparation for Roland Garros."

Williams had been a perfect 5-0 lifetime versus Kvitova. The two women were scheduled to meet in a quarterfinal here in Madrid last year, but Williams pulled out of the match with a thigh injury.

The 33-year-old Williams was playing in only her third WTA tournament since clinching her sixth Australian Open title and 19th Grand Slam singles championship back in January.

She captured back-to-back titles in Madrid in 2012 and 2013.

An all-Russian semi saw the unseeded two-time Grand Slam champion Kuznetsova send the third-seeded former world No. 1 Sharapova packing, 6-2, 6-4.

"Today she had much more pop on her ball than I did, while I felt my shots were a bit too flat," Sharapova said. "I also think the court and the bounce, with the altitude here, meant her spin was getting really high."

Kuznetsova is now 5-8 lifetime versus Sharapova, who had won their last four meetings.

The reigning French Open champ Sharapova topped Romanian Simona Halep in last year's Madrid final and was the 2013 runner-up here to Williams.

Saturday's final will see the world No. 4 Kvitova and 29th-ranked Kuznetsova meet for a fifth time at the WTA level, with the Czech holding a 3-1 lifetime advantage. Kuznetsova, however, captured their last meeting in the third round at last year's French Open.

The 25-year-old left-handed Kvitova will appear in her 21st career WTA final, seeking a 16th title. She was a winner in Sydney in January.

The 29-year-old Kuznetsova is 14-20 in her career finals, with her last title coming in Washington, D.C., last year.