Elena struggles into semis. Kirilenko Beats Safina

A day before she said it was "a great opportunity", and she certainly meant it. In just 53 minutes Nadia Petrova sent the Pilot Pen Tennis at Yale's No.2 seed Samantha Stosur packing in a hurry, 6-2 6-1.

Petrova, seeded No.8, was broken in the first game of the match but was almost perfect on serve from there, losing a total of just three points in her other six service games and breaking the big-serving Stosur five times. Petrova has now beaten Stosur in straight sets in all four of their career meetings.

"It seemed surprising, those are the right words," Petrova said. "I know Sam well. We played the first six months of the year in doubles and I got a lot of time to practice with her, so I know her game well, her strengths and weaknesses.

"Today I was really in charge of the game and didn't give her any chances to come back. I just kept the pressure on and tried to make her come up with a better shot. I'm very happy with my serve and didn't give out many free points."

"We both had our game plans, except she executed hers a lot better than me today," Stosur said. "I got off to a good start. She can ride on confidence really well though, and when she feels she's in front and can control what's going on, she's very hard to stop. She played quite well and I didn't play very well, so me winning only three games is probably a mixture of those two things."

Next up for Petrova is Maria Kirilenko, who ended the run of former No.1 Dinara Safina with a 6-3 6-3 win. Safina had beaten No.3 seed Francesca Schiavone and Daniela Hantuchova before running into Kirilenko, who has been creeping up the rankings all year and is approaching the Top 20 again.

"It's difficult for Dinara to come back. Before she was more aggressive, but now she's making longer points, and it's not hurting you as much," Kirilenko said. "I played well today, not many mistakes and very consistent. Everything was perfect today, except my serve. I missed too many first serves."

Petrova and Kirilenko are tied in their head-to-head, 3-3. This will be their first meeting on the Sony Ericsson WTA Tour in almost exactly two years.

In the other semifinal, No.1 seed Caroline Wozniacki will play No.4 seed Elena Dementieva. Wozniacki advanced to the semifinals when No.7 seed Flavia Pennetta had to withdraw due to a right foot injury; Dementieva battled for three hours to get past No.6 seed Marion Bartoli, 6-3 3-6 6-2.

"I never like to withdraw but my foot has been bothering me since last week and I knew I wouldn't be able to finish the match; I decided to pull out and not risk any further damage," Pennetta said. "The good news is there's no stress fracture. The toe on my right foot is just very inflamed. With some rest and lots of physiotherapy in the next few days, I hope to be ready for the US Open."

Dementieva leads Wozniacki in their head-to-head, 3-2.