The 2018 champion faced compatriot Misaki Doi in a late-night first round encounter, emerging with a 6-2 5-7 6-2 victory.

Having retired from the Cincinnati final a few days ago, there were questions regarding Osaka's health leading up to this match. However, the Japanese superstar showed no signs on injury as she quickly broke her opponent to race to a 3-1 lead. A second break soon followed, and Osaka wrapped up the first set without much difficulty.

Nonetheless, Doi fought back in the second set, coupled with a dip in form by her higher-seeded countrywoman. Doi obtained an early break to lead 2-0, and soon served for the set at 5-3. Osaka broke back to level things at 5-5, but failed to force a tiebreak and Doi escaped with the second set.

It was all Osaka in the final set however, as she dominated her opponent to secure the crucial break. A second break saw Osaka serve for the match at 5-2, and she clinched the victory on her second match point. She next faces Camila Giorgi, who rallied from a set down to defeat Alison Van Uytvanck 2-6 6-1 7-5.

Eleventh seed Elena Rybakina had an easier time in her opening round match, securing a convincing 6-3 6-0 victory over Katarina Zavatska. She will face American Shelby Rogers, who defeated Irina Khromacheva 6-2 6-2.

Jennifer Brady also advanced to the second round, defeating Russian Anna Blinkova 6-3 6-2 after 76 minutes. She next faces compatriot Cici Bellis, who overcame Tamara Korpatsch 6-7(13) 6-3 6-2 in her first round match.