Back injury sidelines Serena Williams

ROME, May 16 (UPI) -- Maria Sharapova won Friday's last quarterfinal match at the $1.34 million Italian Open in Rome with a 6-7 (3-7), 7-5, 6-2 win over Patty Schnyder.

The second-seeded Sharapova needed nearly three hours to eliminate her ninth-seeded foe by coming back from a first set tie-breaker loss. She overpowered Schnyder late in the second to win the match.

Fifth-seeded Serena Williams opted out of her match against unseeded Alize Cornet of France after sustaining an injury during practice.

"It happened all of a sudden," Williams said. "I went for a shot and then my back got a little stuck. I tried to wait until the last possible moment to see if I could play."

Jelena Jankovic, the fourth seed, defeated No. 7 seed Venus Williams, 5-7, 6-2, 6-3, while Russia's Chakvetadze ousted Tsvetana Pironkova of Bulgaria, 6-2, 3-6, 6-1.

In Saturday's semifinals, Sharapova plays Jankovic and Chakvetadze faces Cornet.

Sunday's champion will earn $196,900.