By Tom Perrotta

Elena Dementieva (RUS) [5] vs. Nadia Petrova (RUS) [21] Centre Court: 1:00 pm

Both Dementieva and Petrova have reached the Wimbledon quarterfinals before. Today, one of them will reach her first semifinal. Petrova’s strong serve, athleticism, and skill in the forecourt are perfect for grass. Dementieva seems a less likely candidate for grass court success, especially with her weak serve. But remember that she hits the ball as flat (and as hard) as any player in the world and has a low strike zone. She can move, too. The real question is, who will have the first meltdown, and will it decide the match?

Prediction: Petrova

Serena Williams (USA) [6] vs. Agnieszka Radwanska (POL) [14] Centre Court: 2nd match

Radwanska is a battler and a botherer, and those qualities can work against Serena Williams, who played her best match of the tournament against Bethanie Mattek but still seems to lack the conviction she once had at the All England Club. Nonetheless, she’s the heavy favorite against a talented youngster who lacks weapons.

Prediction: Williams

Venus Williams (USA) [7] vs. Tamarine Tanasugarn (THA) [15] Court 1: 1:00 pm

When asked to assess her match against Venus Williams, Tanasugarn said, “Uhm, I play her many times and she kick my butt.” This is going to be another one of those times. Congrats to the 31-year-old Thai for reaching her first Wimbledon quarterfinal (after seven trips to the fourth round). The road ends here as Venus moves a step closer to her fifth Wimbledon title.

Prediction: Williams

Nicole Vaidisova (CZE) [18] vs. Zheng Jie (CHN) Court 1: 2nd match

In a tournament full of surprises, Zheng, a 24-year-old doubles expert, is the most surprising of all. Vaidisova ought to knock Zheng around the court; she has a lot more offense and a superior serve. Somehow, though, I don’t think she'll succeed in doing what ought to be simple to do. Zheng moves exceptionally well and doesn’t make many mistakes. She is, like Radwanska, a pest (and I mean that as a compliment). If you pester Vaidisova long enough, there’s a good chance she’ll implode.

Prediction: Zheng (if for no other reason that this tournament needs one last upset)