Williams and Clijsters face off for 13th time, Wozniacki up first

For Venus Williams and Kim Clijsters, today is Friday the 13th. The two have squared off 13 times overall and four times at the US Open.

Tied in head-to-head at 6-6, the question is, who's lucky day will it be?

Williams takes the court today hoping to make her fourth United States Open final, and first since 2002. Her opponent, Clijsters, is hoping to put herself in a position to be the first reigning champion to successfully defend her title since Williams did it in 2001.

The first time they met in Flushing, in 2001, Williams was 21 years old and Clijsters was 18. Williams won and went on to defeat her sister, Serena, for her second consecutive US Open title. Clijsters turned the tables in 2005, defeating Williams en route to her first Grand Slam title, and topped her again last year en route to her second championship.

Head-to-head, the two are tied 6-6, but Clijsters has won the last four matchups.

Who has the advantage here? Both play similar games anchored by powerful ground strokes, with Williams perhaps having a slightly better serve and Clijsters a bit more consistency off the ground. Both have a history of losing focus at times, going through stretches where errors come in bunches. But at this point in the tournament, it is hard to imagine they will be anything but dialed in.

Williams played in three consecutive US Open singles finals to start the century, winning the title in 200 0 and 2001 and losing to her sister in 2002. She has not, however, returned to the final since.

The closest she has come since has been the semis in 2007. With a victory today, Williams will set the Open Era record for longest stretch between appearances in the women’s singles final, at eight years.

The undercard in the women’s semifinals features Vera Zvonareva vs. Caroline Wozniacki.

At Wimbledon Zvonareva beat three seeded players, including Clijsters, before losing in the final to Serena Williams.

Wozniacki has been locked in from the beginning, moving into the semifinals without dropping a set. Despite her youth, she is a top tactician, and now she has the fitness and offensive weapons in her still-maturing game to stay with Zvonareva shot for shot.