A day after saying she was "not really that comfortable" playing on grass, top-ranked Naomi Osaka needed three sets to get past her first-round opponent at the Birmingham Classic on Tuesday.

Osaka lost the second set to Maria Sakkari of Greece before recovering to win 6-1, 4-6, 6-3, for only her 11th tour-level victory on grass.

"I was kind of screaming on the inside during that entire match," Osaka said in her on-court interview. "I got lucky a little bit, I guess."

Osaka has yet to make it past the third round at Wimbledon, which starts on July 1.

"I felt better than the two practice days," Osaka said. "And I feel every day that I play on grass of course I'm going to learn how to play better, but for now I'm just really happy I was able to win that match."

Osaka needs to reach the final in Birmingham to guarantee holding on to top spot in the rankings heading into Wimbledon.

"During my entire clay season, it kind of mattered and I think it showed because I was kind of stressed out the entire time," she said. "So, now, I'm just having fun. I'm enjoying it. And I know that if I play well, then I'll be No. 1."

Osaka will next face Yulia Putintseva, who defeated Britain's Harriet Dart 6-1, 6-4.

Rain washed out much of the schedule Tuesday, with second-seeded Ashleigh Barty — the newly crowned French Open champion — among those who will have to try again on Wednesday.

Julia Goerges recovered to defeat Dayana Yastremska 3-6, 6-3, 6-4 while former French Open champion Jelena Ostapenko eased past Wimbledon junior champion Iga Swiatek 6-0, 6-2 and will now face Johanna Konta.

Kristyna Pliskova of the Czech Republic set up a first tour-level meeting with her twin sister, Karolina, by defeating Viktoriya Tomova 6-3, 6-4.