Former Wimbledon champion Garbine Muguruza earned a 6-3, 6-4 win over Carla Suarez Navarro on Monday after a day interrupted by rain at the Sydney International.

Sam Stosur, the 2011 U.S. Open champion, had a rare win on Australian soil when she rallied to beat Dominika Cibulkova 3-6, 6-3, 6-4, a confidence-boosting result for the local hope ahead of the Australian Open, which starts next week.

Seventh-seeded Kiki Bertens beat Bernada Pera 7-5, 6-4, Timea Bacsinszky ousted ninth-seeded Anastasija Sevastova 6-7 (3), 6-4, 6-4, Yulia Putintseva beat Daria Gavrilova 6-1, 7-6 (4), and Camila Giorgi defeated Ajla Tomljanovic 6-3, 6-3 in other first-round matches.

On the men's side, Japanese qualifier Yoshihito Nishioka beat Ryan Harrison 6-4, 6-2 and 2018 finalist Alex De Minaur defeated Dusan Lajovic 6-4, 6-3.

"It wasn't easy all day, a lot of waiting around, especially coming in so early and the weather not permitting us to go out and play," de Minaur said. "I'm happy with how I dealt with the situation and really happy with the win."

De Minaur lost last year's final to Daniil Medvedev, who announced Monday he wouldn't attempt to defend the title after losing to Kei Nishikori in the Brisbane International final the previous day.

Sam Querrey was leading 6-1, 4-1 when Malek Jaziri retired from their match, and he advanced along with Reilly Opelka and Guido Andreozzi.