For the first time since 2008, the New Haven Open champion will be someone other than four-time defending champion Caroline Wozniacki.

Wozniacki retired from her semifinal match with No. 7 seed Maria Kirilenko this afternoon, ending her 20-match winning streak in the Elm City. Kirilenko advances to the final, where she will meet No. 2 seed Petra Kvitova in a rematch of their London Olympics quarterfinal match, which Kirilenko won.

In her match against Kirilenko, Wozniacki’s right knee was taped due to an injury sustained in her quarterfinal match on Thursday. That injury prompted Wozniacki to retire after dropping the first set 7–5. According to the four-time champion, she was not fully fit and wanted to make sure she enters the US Open at full strength. Kirilenko’s victory was her first in six attempts against Wozniacki.

“It’s definitely not the way I would have liked to have finished here, having won four times,” Wozniacki said in a press conference. “I would have loved to just play a normal match.”

The only set of the match took 49 minutes and its result rested on the pivotal 11th game. With Wozniacki serving at 5–5, Kirilenko ripped two backhand winners and benefited from a long Wozniacki backhand to jump in front 15–40. The two break points were the first in the match for either player. Wozniacki saved the first with deft touch and agile movement, as both players ended up trading drop shots at the net. Although Wozniacki also saved the second with a strong serve down the T, Kirilenko would not be denied. She pounded a forehand return winner down the line off Wozniacki’s wide serve at deuce to capture a third break point opportunity. On the next point, Wozniacki’s backhand sailed wide and long, putting Kirilenko up 6–5 in games. In the next game, she served out the set.

Kirilenko is at a career-high ranking of world No. 14. At the London Olympics, she took fourth place in singles and won a bronze medal in doubles. The final in New Haven will be Kirilenko’s first ever at a North American tournament.

Both Kirilenko and Wozniacki attributed some of Kirilenko’s recent success to the progress of her serve.

“It’s important that my serve has improved, so I[’m] really happy I found a rhythm…, a right technique to serve,” Kirilenko said. “It’s helpful.”

In the day’s other semifinal, Kvitova, Wimbledon champion in 2011, made quick work of No. 4 seed Sara Errani, 6–1, 6–3. Kvitova continually exploited Errani’s weak second serve, which consistently floated in around 70mph. Kvitova hit several return winners off both wings.

“About the return, I always step in the court and try to attack from the return because Sara didn’t have the fastest speed on the tour,” Kvitova said after the match.

Kvitova, who won the Rogers Cup in Montreal just two weeks ago, used all aspects of her game in the 24-minute first set. After breaking Errani in the second game to go up 2–0, Kvitova seemed to gain steam. She ended the set by winning its final ten points, both breaking and holding at love.

Errani attempted to fight back in the second set by hitting harder. Her strategy was moderately successful. Although she was broken in the first game of the set, she managed to hold serve three times. Still, Errani had to fight just to hold, and each hold went to deuce at least once. Errani simply had to go for more than she was used to.

“If I try to hit more strong, maybe I make more fault,” Errani said. “But I have to try everything.”

Since her Wimbledon quarterfinal against Kirilenko, Kvitova has had more hard court success than any other woman on tour. In fact, Kvitova amassed the most US Open Series points over the course of the hard court season. If she wins the U.S. Open, Kvitova will receive a $1 million bonus as a prize for winning the U.S. Open Series in addition to the $1.9 million winner’s check for the U.S. Open itself.

Kirilenko and Kvitova will play the final of the New Haven Open Saturday at 3 p.m.