Ukraine SSR, Soviet Union, modern day Ukraine) turned professional in 2002 and reached a career high ranking of 13 in singles in 2017 and number 1 in doubles in 2018. Vesnina's best result in a Grand Slam came at the 2016 Wimbledon championships, where she fell to Serena Williams in the semifinals in straight sets. She also won three WTA singles titles during her career. Her biggest success was in doubles, with 3 Grand Slam women's doubles titles alongside Ekaterina Makarova at the 2013 French Open, the 2014 US Open and at Wimbledon in 2017, as well as the mixed doubles title at the 2016 Australian Open alongside Bruno Soares. She also partnered Makarova to gold in the women's doubles at the 2016 Olympics, and to the title at the WTA Finals, both in 2016. Vesnina had been absent from the WTA Tour since 2018 following the birth of her daughter. Kim Clijsters (born 8 June 1983 in Bilzen, Belgium) initially entered the 2021 Miami Open, but pulled out, saying she did not feel ready to compete after her surgery and contracting COVID-19 in January. She played her first tournament of the year at the 2021 Chicago Fall Tennis Classic after accepting a wildcard, but lost in the first round to Hsieh Su-wei. Retirements The following is a list of notable players (winners of a main tour title, and/or part of the WTA rankings top 100 in singles, or top 100 in doubles, for at least one week) who announced their retirement from professional tennis, became inactive (after not playing for more than 52 weeks), or were permanently banned from playing, during the 2021 season: Gréta Arn (born 13 April 1979 in Budapest, Hungary) joined the professional tour in 1997 and reached a career-high ranking of No. 40 in singles in May 2011 and No. 175 in doubles in December 2000. She won two singles titles in her career. Timea Bacsinszky (born 8 June 1989 in Lausanne, Switzerland), has won four WTA singles titles in her 15-year career, where she reached a career high of No.9, and five doubles titles. She reached the semifinals of French Open in singles in 2015 and 2017. She also won a silver medal in doubles with Martina Hingis at 2016 Rio Olympics. Bacsinszky announced her retirement on 16 July due to constant injuries. Kiki Bertens (born 10 December 1991 in Wateringen, Netherlands) turned professional