Note: US Open 2009 4th round 156 // Carolinewozniacki // Caroline Wozniacki
2011: Year-end No.1 for the second year in a row
During the off season, Wozniacki switched her racquet make from Babolat to Yonex. Wozniacki began her 2011 season with an exhibition match in Thailand against Kim Clijsters where she lost in a super tie-break. Wozniacki then played another exhibition, the team Hong Kong Tennis Classic, where she represented and was captain of Team Europe. She won two matches against Team Asia Pacific, before getting crushed by world no. 2 Vera Zvonareva in the final against Team Russia. Her first WTA tournament was the Medibank International Sydney. She received a bye to the second round, where she lost to Dominika Cibulková.
Wozniacki dropped to no. 2 behind Kim Clijsters during the week of 14 February, but regained the top spot the following week. She received a bye to the second round in Dubai where, in the quarterfinals, she beat Shahar Pe'er to ensure her no. 1 position in the next rankings update. She went on to defeat Svetlana Kuznetsova in the final to take her 13th career singles title and first of the year. In Doha, she received a bye to the second round and reached the final, after defeating Nadia Petrova, Flavia Pennetta, and Marion Bartoli in straight sets. She lost to Vera Zvonareva in the final. In the first Premier Mandatory event of the year in Indian Wells, Wozniacki made it to the final, where she defeated Marion Bartoli for her 14th singles title. After a first-round bye at the Sony Ericsson Open in Miami, Florida, Wozniacki lost in the fourth round to 21st seed Andrea Petkovic. Wozniacki made an uncharacteristic 52 unforced errors and later said she had been playing a lot of matches when she was asked about fatigue. In the Family Circle Cup, Wozniacki made it to the final, where she defeated unseeded Elena Vesnina to take her third title of the year, 15th of her career. In Stuttgart, Wozniacki made it to her fifth final of the year, where she lost to Julia Görges in straight sets. In Madrid, Wozniacki lost to Görges again, this time in the third round. In Rome, she lost to eventual champion Maria Sharapova in the semifinal round. At the Brussels Open, Wozniacki reached the semifinals, where she defeated third seed and reigning French Open champion, Francesca Schiavone. In the final, Wozniacki's sixth of the year, she defeated eighth seed Peng Shuai to win her first red clay title, after having won three on the faster green clay. Wozniacki was the top seed at the French Open, but was defeated in the third round by 28th seed Daniela Hantuchová.
Wozniacki's next tournament was the e-Boks Sony Ericsson Open in her native Denmark. In the final, she defeated fourth seed Lucie Šafářová, taking her fifth title of the year. At Wimbledon, she had straight-set wins until the fourth round, but then lost to 24th seed Dominika Cibulková.
At the Rogers Cup Wozniacki made an early second-round exit. She was defeated by Roberta Vinci in straight sets despite holding a 5–1 lead in the second set. Wozniacki was the top seed at the Western & Southern Open in Cincinnati, but lost in the second round to world no. 76 Christina McHale. Next playing at the New Haven Open at Yale, Wozniacki won the title for the fourth year in a row, defeating Francesca Schiavone in the semifinals and qualifier Petra Cetkovská in the final.
At the US Open, Wozniacki was the first seed. In the first round, she defeated Nuria Llagostera Vives. In the second round, Wozniacki defeated Arantxa Rus, and in the third round, defeated American Vania King. In the fourth round, Wozniacki fought back from a 7–6, 4–1 deficit, defeating Svetlana Kuznetsova. Wozniacki then progressed to the semifinals by defeating Andrea Petkovic in the quarterfinals. In the semifinals she lost to Serena Williams.
Wozniacki was the top seed at the WTA Championships. In the group stage she beat Agnieszka Radwańska before falling to Vera Zvonareva. She lost also to Petra Kvitová in her final round-robin match and so she failed to advance to semifinals for the first time in three appearances. She finished the year as world no. 1 for the second consecutive year. Despite narrowly edging Petra for the Year End #1 ranking in points, she lost out on all Player of Year awards to Petra.
2012: Beginning of singles decline
Wozniacki began her season by representing Denmark at the 2012 Hopman Cup with Frederik Nielsen as her partner. Wozniacki won two of her three round robin matches in singles, defeating Bethanie Mattek-Sands and Tsvetana Pironkova before losing to world no. 2 Petra Kvitová.
Wozniacki's first WTA event was the Apia International Sydney. After a first round bye, Wozniacki defeated Dominika Cibulková after trailing 4–0 in the third set. She lost to Agnieszka Radwańska in three sets in the quarterfinals, after serving for the match at 5–4 up in the second set.
Wozniacki competed at the Australian Open as the top seed. She defeated Anastasia Rodionova, Anna Tatishvili, Monica Niculescu, and Jelena Janković, all in straight sets, to reach the quarterfinals where she lost to the defending champion Kim Clijsters. As a result, Wozniacki lost her top ranking and was replaced by the 2012 champion Victoria Azarenka. Next playing at Doha, Wozniacki lost to Lucie Šafářová in the second round, having received a first round bye.
Wozniacki reached the semifinals in Miami after beating Barbora Záhlavová-Strýcová, Petra Cetkovská, Yanina Wickmayer, and Serena Williams, all in straight sets. Wozniacki then lost to second seed Maria Sharapova. Wozniacki did not defend her title in Charleston as she was not allowed to participate under WTA rules because two top-6 players had already entered the draw. Wozniacki then played her home tournament in Copenhagen. She reached the final but lost to Angelique Kerber, her first loss at the tournament since the start in 2010.
Wozniacki represented Denmark at the Olympics as the eighth seed in the women's singles event. In the first three rounds she defeated Anne Keothavong, Yanina Wickmayer and Daniela Hantuchová. She was then defeated by the eventual champion Serena Williams in the quarterfinals.
Wozniacki next participated in the Rogers Cup where she lost to Petra Kvitová in the semifinals, and the Western & Southern Open where she was defeated in the third round by Anastasia Pavlyuchenkova. As the four-time defending champion at the New Haven Open at Yale, Wozniacki retired against Maria Kirilenko in the semifinals due to a right knee injury, which she had suffered in her quarterfinal win over Dominika Cibulková.
Wozniacki, still suffering with the injury, was seeded eighth at the 2012 US Open, but did not advance past the first round. She lost in two sets to 96th-ranked Romanian Irina-Camelia Begu. As a result of the loss, Wozniacki dropped out of the top 10 for the first time in three years.
Following her US Open disappointment, Wozniacki won her first tournament of the year in Seoul by defeating Arantxa Rus, Caroline Garcia, Klára Zakopalová, Ekaterina Makarova, and Kaia Kanepi in the final. It was her 19th career title.
Wozniacki's next tournament was the Kremlin Cup. As the third seed in the tournament, she defeated top seed Samantha Stosur in the final in 3 sets to take home her second title of the year, and 20th overall.
In December 2012, during an exhibition match in Brazil, Wozniacki imitated friend and fellow tennis player Serena Williams by stuffing towels in her shirt and skirt in order to appear to be large-chested and have a large rear end. This act divided opinion on social network sites. It was noted that Wozniacki has done the impression before without controversy. Williams also defended Wozniacki in an email to USA Today and pointed out that they are friends and that the act was not racist. Williams added however, that if people feel this way then she should do something else next time.