Kerber a surprise U.S. Open semifinalist

NEW YORK, Sept. 9 (UPI) -- Serena Williams will take on top-seeded Caroline Wozniacki in a semifinal matchup that was expected at the U.S. Open but the other women's semi wasn't foreseen.

Williams is 20-2 since returning from a near yearlong layoff caused by injuries. Even though she was seeded 28th, Williams entered the Open as the favorite. Saturday will mark her 20th Grand Slam semifinal. She is 16-3 in those matches.

Wozniacki is coming off a tournament win at New Haven, Conn., her sixth title this year. However, she's never won a major tournament -- only making one final -- 2009 at the U.S. Open -- even though she's held the No. 1 ranking for the last 30 weeks and 48 weeks overall.

Williams is 2-0 in their previous meetings, which were both in 2009.

While that semifinal could have been predicted two weeks ago when the draws were announced, the bottom half of the draw delivered a big surprise.

Ninth-seeded Samantha Stosur knocked off second-seeded Vera Zvonareva 6-3, 6-3 in the quarterfinals for her third Grand Slam semis appearance. She lost the title match at the 2010 French Open.

Her opponent is Angelique Kerber, who'd never been beyond the third round of a major tournament before this week and began the tournament with a No. 92 ranking. Kerber beat 26th-seeded Flavia Pennetta in a tough three-set match Thursday.

Kerber and Stosur have never before met on the court.

The winners meet Sunday for the championship.

Williams will be looking for her fourth U.S. Open title -- she won in 1999, 2002 and 2008 -- and 14th overall Grand Slam championship. A win Sunday by any of the other three semifinalists would mark a first major tournament title for that player.