DUBAI, United Arab Emirates (AP) -- Emma Raducanu lost in the second round at the Dubai Championships to Karolina Muchova 7-6 (6), 6-4 on Tuesday.

The 2021 U.S. Open champion, who appeared to be in tears as she went to the umpire's chair after the second game, fell behind 4-0 before forcing a tiebreaker.

Raducanu was broken again in the first game of the second set. After failing to convert any of the three break points she earned in the sixth game, it was Muchova who prevailed 6-4.

The 14th-seeded Muchova will next face McCartney Kessler, who earned her first top-10 victory by beating third-ranked Coco Gauff 6-4, 7-5.

Gauff hadn't fallen to an opponent ranked outside the top 50 since a loss to Sofia Kenin (128th) at Wimbledon in 2023. Kessler is ranked No. 54.

Earlier, second-seeded Iga Swiatek beat Victoria Azarenka 6-0, 6-2 and will next face Dayana Yastremska for a spot int the quarterfinals.

Top-seeded Aryna Sabalenka eliminated Veronia Kudermetova 6-3, 6-4, and defending champion Jasmine Paolini defeated Eva Lys 6-2, 7-5.

Elena Rybakina , Jessica Pegula and Paula Badosa also advanced.

AP tennis: https://apnews.com/hub/tennis