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Introduced to tennis at five, Kateryna Kozlova admired Martina Hingis and Roger Federer. If not a tennis player, would have been a psychologist or hip-hop dancer.
She made her professional debut at $10K ITF in Kharkiv in 2008. Then she played her first WTA qualifying match at 2012 Tashkent and main draw match at 2013 Baku (d. Daniildou, l. Voskoboeva).
In 2015 she contested 10 WTA main draws in 2015, progressing beyond the first round in Hobart, Dubai, Kuala Lumpur, and
Tashkent, where she reached the quarter-finals (l. Hibino). That year, she also made her Grand Slam main draw debut at US Open, losing to Mattek-Sands in the opening round.
2016 season saw her reach her first tour-level semifinal, at Istanbul (l. eventual R-Up Kovinic) and Tashkent (l. eventual champion Kr.Pliskova). Also made quarterfinals stage at Premier-level St. Petersburg (as qualifier, l. Ivanovic) and 's-Hertogenbosch (l. Brengle). She ended the season at No.99.
She posted her career-best year-end finish of No.86 in 2017. Tour-level highlights were the quarter-finals run in Bastad (as qualifier, l. Wozniacki) and the second-round run at US Open (as qualifier, l. Sevastova). She also won the title at WTA 125K Series event in Dalian (d. Zvonareva) and at $60K ITF event in Rome (d. Duque-Mariño).
Early in 2018, she was runner-up in Taipei City (l. Babos) in her first WTA final in either singles or doubles. Afterwards she reached her career-high ranking of No.62. At Roland Garros, she beat the defending champion, Jelena Ostapenko, to clinch her maiden Top 30 win of her whole career.