Wozniacki started her preparation for the Australian Open at the ASB Classic in Auckland seeded as No. 1 and advanced to the final before losing to Venus Williams in three sets. Despite being seeded eighth at the Australian Open, Wozniacki was unfortunate to draw fellow former world number one and two-time champion Victoria Azarenka in the second round, and was defeated in straight sets.[11] After the tournament, she climbed back up to No. 5.[12] Wozniacki then competed at the Dubai Tennis Championships where she made it all the way to the semifinals before losing to eventual champion Simona Halep in three sets. Wozniacki's next tournament was the Qatar Total Open where she was seeded second. However, she lost once again to fellow former No. 1 Victoria Azarenka in the quarterfinals in straight sets, winning just four games. She rebounded at the Malaysian Open, winning the title by defeating Romanian Alexandra Dulgheru in the final in three sets.
Wozniacki's next tournament was the BNP Paribas Open where she was seeded fourth. In the second round, she beat Ons Jabeur before losing in the third round to Belinda Bencic in straight sets. She then competed at the Miami Open beating Madison Brengle in the second round and Kaia Kanepi in the third round. She lost to Venus Williams in the fourth round in straight sets.
Wozniacki started her clay season in Stuttgart where she was seeded fourth. In the second round, she beat Lucie Šafářová in straight sets. In the quarterfinals, she dropped just three games against Carla Suárez Navarro to advance to the semifinals. In the semifinals, she beat Simona Halep in a three set thriller to reach her first clay court final since 2011. She lost to Angelique Kerber in the final in three sets, despite serving for the match in the third set. Wozniacki's next tournament was the Mutua Madrid Open where she made it to the quarterfinals for the first time since 2009 beating 娅尔米拉·盖多绍娃, Christina McHale, and Agnieszka Radwańska. She lost in the quarterfinals to Maria Sharapova in three sets. Wozniacki's next tournament was the Internazionali BNL d'Italia. She lost in the second round to Victoria Azarenka for the third time in straight sets. Wozniacki then played at the French Open as the fifth seed. She beat Karin Knapp in straight sets before losing to Julia Görges in the second round in straight sets.
Wozniacki started her grass season at the Aegon International. She beat 娅尔米拉·盖多绍娃 in straight sets and Svetlana Kuznetsova in three sets to advance to the quarterfinals. She beat Andrea Petkovic in straight sets to advance to the semifinals where she faced Belinda Bencic. She retired from the match due to a back injury after losing the first three games. Wozniacki then played at Wimbledon as the fifth seed. She beat Zheng Saisai in straight sets after being down 1–4 in the first set. After beating Denisa Allertová, she breezed past Camila Giorgi to advance to the fourth round and lost to eventual finalist Garbiñe Muguruza in straight sets. Despite the loss, Wozniacki climbed back up to No. 4 after the tournament.
Wozniacki's summer hard court season got off to a slow start due to an ankle injury. This injury caused her to lose early at Stanford, Toronto and Cincinnati to Varvara Lepchenko, Belinda Bencic and Victoria Azarenka, respectively. Wozniacki then played at the Connecticut Open. She finally picked up her first win by crushing Alison Riske in the first round. She then beat Roberta Vinci in three sets after being down 3–5 in the third set, saving 3 match points in the third set tiebreak, to advance to the quarterfinals. She breezed past Caroline Garcia before losing in the semifinals to Petra Kvitová in straight sets. Wozniacki then played at the US Open as the fourth seed. She easily beat Jamie Loeb in her opening match to advance to the second round where she was upset by Petra Cetkovská in a close three set match despite having four match points.
Wozniacki began her Asian hard court swing at the Toray Pan Pacific Open. As the top seed, she received a bye in to the second round where she easily beat Ana Konjuh. She then defeated Angelique Kerber in three sets in the quarterfinals. In the semifinals, she lost to Belinda Bencic for the fourth straight time in straight sets. Wozniacki's next tournament was the Wuhan Open. She lost to Anna Karolína Schmiedlová in the second round in three sets, despite being up a set and a break. Wozniacki's next tournament was the China Open. She beat Bojana Jovanovski in the first round, and won ten games in a row to beat Qiang Wang to advance to the third round. She lost to Angelique Kerber in straight sets. The loss ended Wozniacki's chances to qualify for the WTA Finals.
At the WTA Elite Trophy, Wozniacki was drawn into Group D alongside Roberta Vinci and Svetlana Kuznetsova. After retiring in her first match against Svetlana Kuznetsova, Wozniacki withdrew from the tournament. She finished the year ranked at No. 17, her worst year-end ranking since 2007.
Wozniacki began her 2016 season at the ASB Classic in Auckland, where she was defending finalist points. After beating Danka Kovinić in straight sets, she dropped a combined three games against Christina McHale and Alexandra Dulgheru to advance to the semifinals where she lost to eventual champion Sloane Stephens in straight sets. Wozniacki's next tournament was the Australian Open where she lost to Yulia Putintseva in the first round in three sets, marking her worst performance at the tournament. Wozniacki's next tournament was the St. Petersburg Ladies' Trophy. She lost to Dominika Cibulková in the second round in straight sets. Wozniacki next played the Qatar Open for which she needed 9 match points to beat Ana Konjuh in the first round. She was at one point up by a double break in the third set. In the second round, she faced Daria Gavrilova which she won in straight sets. Wozniacki then played Elena Vesnina in the third round, she fell in a grueling match. Wozniacki played in the 2016 Monterrey Open instead of defending her title in Kuala Lumpur. She defeated Olga Govortsova in the first round and Mirjana Lucic-Baroni in the second round; however, she fell in the quarterfinals to the eventual winner Heather Watson. Caroline then played at the BNP Paribas Open and fell in the second round to Zhang Shuai. This match marked the longest match so far in 2016, at 3 hours and 24 minutes. Then in the 2016 Miami Open Wozniacki made a promising start, defeating Vania King; however, she fell to twelfth seed Elina Svitolina.
Wozniacki was scheduled to play many clay court tournaments. However, she injured her ankle during a practice, which put her out for all of the clay-court season. This break saw Wozniacki fall though the rankings from 22 down to 34, the lowest since May 2008. She withdrew from 2016 French Open because her ankle was not 100%.
Wozniacki played in Nottingham, her first tournament since the Miami Open in March and her first tournament after hiring her new coach David Kotyza. Wozniacki won her first match in ten weeks defeating Çağla Büyükakçay, but falling in yet another three-set match to Anett Kontaveit in the second round. In her last tournament leading up to Wimbledon, Wozniacki played the 2016 Aegon International Eastbourne. She showed signs of improvement from her loss of form and injury, dismissing Alizé Cornet and seventh seed Samantha Stosur and dropping only seven games in the two matches before losing in a three-set match to qualifier Monica Puig. In Wimbledon, she went unseeded in the tournament, the first time since 2008 Australian Open and lost to Svetlana Kuznetsova in the first round, resulting in her falling out of the top 50 for the first time since February 2008.
Wozniacki began her US hard court season in Washington, playing the 2016 Citi Open she went on to beat Hiroko Kuwata in the first round and retired in her second round clash with Samantha Stosur despite being up a set 7–5 a sharp pain in her left arm forced her to retire. This injury also took her out of The Rogers Cup. She then played the Summer Olympic Games. Dropping four games she beat Lucie Hradecka but fell to Czech Petra Kvitová in the second round. She failed to win a match in the Connecticut Open as she lost in the first round to young Latvian Jelena Ostapenko. However, Wozniacki's year turned around at the 2016 US Open. She slid past Taylor Townsend in three sets, then upset Svetlana Kuznetsova in round two after being two breaks down she came back to win in straight sets. She then beat Monica Niculescu in two sets to reach the fourth round, in which she upended Madison Keys in two sets to reach the quarterfinals and then beat unseeded Anastasija Sevastova to enter the semifinals.[13] Wozniacki lost the semifinal to then-new No. 1 Angelique Kerber, in two sets, and resulting at the back of the top 30 for the first time since April of this year.[14]
Wozniacki moved on to the Toray Pan Pacific Open. In the first round, Wozniacki defeated Belinda Bencic, who had defeated her the previous year, in three sets. In the second round, she defeated fourth seed Carla Suarez Navarro, then beat qualifier Magda Linette in straight sets. In the semifinals, Wozniacki defeated defending champion Agnieszka Radwanska, which sent her off to her first final since April of the previous year. In the final, she defeated Japanese player Naomi Osaka to win her 24th WTA title, and her first title since March 2015. This was also Wozniacki's first Premier-level title since 2012.
Wozniacki continued the Asian swing at the 2016 Wuhan Open. There, she had a good start, defeating Samantha Stosur in the first round. In the third round, Wozniacki faced Agnieszka Radwanska again, and this time, Radwanska came out on top. Wozniacki then competed at the China Open. She cruised past her first two matches against Coco Vandeweghe and Roberta Vinci before going head to head with Radwanska for the third time in three weeks. Radwanska emerged victorious again, defeating Wozniacki in straight sets.
After beating Jelena Jankovic in the semifinals, Wozniacki won her 2nd title of the season and 25th title overall, beating Kristina Mladenovic in the final in three sets. This was the first time since 2012 that Wozniacki had won two WTA titles in a single season. With the win, Wozniacki returned to the top 20.
Wozniacki ended the season with a run at the Luxembourg Open. The no. 2 seed had an easy first round win against Madison Brengle, and survived a second round encounter against Sabine Lisicki after losing the first set. She then was forced to retire in the quarterfinals due to sickness. Wozniacki did not play at the 2016 WTA Elite Trophy and ended her topsy turvy season ranked number 19 (having been as low as no. 74).
Wozniacki began the year at the Auckland Open once again. This time, she was the No. 3 seed. She started out strong, breezing past Nicole Gibbs and Varvara Lepchenko before losing in the quarterfinals Julia Görges in three sets, despite being up a set and 3–1. At the Apia International Sydney, Wozniacki was seeded 10th. She played some solid tennis against Olympic Gold Medallist Monica Puig, winning in three sets. Wozniacki then defeated Yulia Putintseva in straight sets in a rematch of their 2016 Australian Open first round clash. In the quarterfinals, Wozniacki was defeated by Czech Barbora Strycova in three close sets, despite being up a break two times in the final set.
Wozniacki was seeded 17th at the Australian Open. She reached the third round, after defeating 阿林娜·罗季奥诺娃 and Donna Vekic, but was defeated by 9th seed and in-form Johanna Konta in a match which lasted just 75 minutes.
Wozniacki and her good friend Serena Williams have met 11 times with Williams leading the head to head 10–1.[17] Williams leads 2–0 in Grand Slams, 8–1 on hard courts, and 1–0 on both clay and grass. Both held the No. 1 ranking from early November 2009 to late January 2012. They are currently the Top 2 active players to hold the No. 1 ranking for the most weeks.
They first met at the 2009 Medibank International Sydney with Williams winning in three tight sets saving match points. Wozniacki's only win over Williams came at the 2012 Sony Ericsson Open where she won in straight sets. In 2014 the rivalry reached its peak with the pair meeting four times and Williams winning all of them. Three of their four meetings went to three sets with Williams coming from a set down in each to win. At the Rogers Cup Wozniacki led by a set and a break before Williams came back to win it. They would meet a week later at the Western & Southern Open where Williams again came from a set down to win. They faced off against each other in the final at the US Open where Williams won in straight sets to claim her 18th Grand Slam title. Their most recent meeting at the WTA Finals was an epic with Wozniacki winning the first set before Williams came back to win the second set. At 4–4 Wozniacki broke Williams to serve for the match and Williams broke back. At 6–5 Wozniacki saved match point with an incredible volley and held serve to take the set to a tiebreak. In the tiebreak Wozniacki was up 4–1 before Williams came back and eventually prevailed.
Despite being rivals, the two maintain a strong friendship off court.[18] Wozniacki visited Williams during her recovery from injury in 2011.[19] In 2014 after they both lost early at the French Open they vacationed together in Miami. They attended a Mariah Carey concert the night before their semifinal match at the WTA Finals. Williams was present during Wozniacki's run at the New York City Marathon. They also went on a mini tour around New York City.[20]
Wozniacki vs. Radwańska
Wozniacki and Agnieszka Radwańska have met 16 times with Wozniacki leading the head to head 10–6.[21] Wozniacki leads 8–6 on hard courts and 2–0 on clay.
They first met at the 2007 Nordea Nordic Light Open with Radwańska winning in straight sets. After that win, Wozniacki would win the next 5 matches before having the streak snapped at the 2012 Apia International Sydney where she lost in three sets. Radwańska would then win the next 2 matches before that streak was snapped at the 2014 Western & Southern Open where she would lose in straight sets. Their most recent meeting was at the 2017 Qatar Total Open where Wozniacki won in straight sets.
Wozniacki vs. Sharapova
Wozniacki and Maria Sharapova have met 10 times with Sharapova leading the head to head 6–4.[22] Wozniacki leads 2–0 in Grand Slams with both coming at the US Open in 2010 and 2014. Wozniacki leads 4–3 on hard courts, while Sharapova leads 3–0 on clay.
The pair first met at the 2008 Qatar Total Open where Sharapova won in straight sets and then again at the 2008 Rome Masters. Wozniacki then won the next two meetings to tie the head-to-head. Sharapova then won the next three meetings including their only meeting in a final at the 2013 BNP Paribas Open. Wozniacki snapped the losing streak by beating Sharapova in three sets at the 2014 US Open and would go on to the reach the final. They met again at the 2014 WTA Finals where Wozniacki won in three sets in a marathon match that lasted over three hours. Their most recent meeting was at the 2015 Mutua Madrid Open where Sharapova won in three sets.