Maria Kirilenko kept her impressive form in 2012 going when she got past Caroline Wozniacki for a chance to play for the title at the New Haven Open. Kirilenko took the opening set 7-5 after an intense battle from both ends. But a right knee injury forced Wozniacki to retire from the match immediately after the first set.

“In the past I had the same problem; sometimes you're moving fine, but some steps it really hurts,” Kirilenko said. “When I'd play a good angle today I saw she didn't run for it. She was for sure having problems - and I think she made the right decision to stop playing today and rest her knee before the US Open.”

“I could feel it from the start, and it started to get a bit worse,” Wozniacki said afterwards. “I decided to stop because if you don't feel 100%, you can't compete at 100%. I wasn't going to win this match anyway if I'm not 100% at a fit level.”

This defeat marked the end of Wozniacki’s unbeaten run here, “It's definitely not the way I would have liked to finish here, having won four times. This event has meant a lot to me. It was a big tournament for me to win back in 2008, then coming back and defending it in 2009 was huge, because it was the first time I had to go and defend a title. Then to defend it again and again, all of a sudden you're in this elite group that has won the same tournament four times. There are a lot of players who never win a title, and a lot of players who never win four titles. What happened this year was unfortunate, but I just need to move on.”

When asked about her US Open prospects, she said, “I'm going to take the rest of the day and tomorrow off and see how it feels, get some treatment on it, ice, then I'll be ready for the Open," she said. "I'll just take it easy these two days.”

In the other semi-final, Petra Kvitova thrashed Sara Errani 6-1, 6-3 to progress to the finals. “I served well tonight and tried to attack the return,” Kvitova said. “I wanted to be the player who took the offensive and hit the winners, because if I just push it back, who knows how it would be.”

“I tried everything, but she was playing incredible on the baseline, hitting so strong without many mistakes. It was difficult,” Errani commented. “Today was not the best for me, but it was a very good tournament for me, reaching the semifinals.”