Host country favorite Naomi Osaka advanced to the second round of the Toray Pan Pacific Open on Tuesday as her Australian opponent Daria Saville had to retire early in the first set with a knee injury.

Saville fell to the court in pain after hitting a forehand in her first service game at Tokyo's Ariake tennis park. It happened after defending champion but unseeded Osaka, ranked 48th in the world, held her serve in the opening game.

Japan's Naomi Osaka (R) looks on as her Australian opponent Daria Saville sits on the court in pain during their first-round match of the Toray Pan Pacific Open tennis tournament in Tokyo on Sept. 20, 2022. (Kyodo)

The former world No. 1 and winner of four Grand Slam singles titles will next face fifth-seeded Brazilian Beatriz Haddad Maia, the 6-4, 6-2 winner over Yuki Naito of Japan.

"I feel really bad right now because obviously how it ended," Osaka said after the match was over in 14 minutes. "I've been injured for most of the year, so I know how it feels. I just want to clap for her because she is a really amazing player."

Osaka had not won a match in her previous three tournament appearances through the U.S. Open.

The Pan Pacific Open has been held for the first time since 2019, following a two-year COVID-19 hiatus.

In other first-round matches, sixth-seeded Karolina Pliskova of the Czech Republic cruised to a 6-2, 6-1 victory over Isabella Shinikova of Bulgaria.

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