MASON, Ohio -- Elena Rybakina stopped playing during the first set of her quarterfinal match against Iga Swiatek at the Cincinnati Open on Thursday night.
Trailing 4-1 and serving at 40-40, the No. 2-ranked Rybakina took a medical timeout to have trainers address her left ankle area.
Rybakina appeared to injure herself during the previous point. After several minutes, she returned to the court but retired from the match after attempting one serve.
Rybakina lost to Swiatek in the semifinals in Cincinnati last year.
With top seed Aryna Sabalenka losing Thursday night to Sara Bejlek, the 27-year-old Rybakina could have risen to No. 1 in the rankings by reaching the final.
Swiatek, the defending champion, has reached at least the semifinals in each of her last four appearances in Cincinnati.