(CNN) Coming into the French Open, Naomi Osaka talked about wanting to win the career grand slam or even calendar year grand slam.

And why not think that big? The hugely talented Osaka has claimed the last two majors and soared to No. 1 in the rankings.

The Japanese megastar could still achieve those goals this year after battling her nerves and escaping against Anna Karolina Schmiedlova in Tuesday's first round match in wet and windy Paris.

Twice in the second set Schmiedlova served for the biggest win of her topsy-turvy career but both times the 90th-ranked Slovak was broken and Osaka prevailed 0-6 7-6 (7-4) 6-1 to narrowly avoid becoming the second women's top seed to lose her opener in Paris.

"I think this is the most nervous I have ever been my entire life during a match," Osaka told reporters. "I think you could see that in the first set. I was literally not hitting any balls in the court.

"For me, today was weird because usually the nerves go away, but it kind of stayed the entire match. Then I just felt like it was a fight of willpower."

Photos: Osaka, Halep win at Roland Garros Naomi Osaka took to center court at the French Open as the top seed at a major for the first time. Hide Caption 1 of 9 Photos: Osaka, Halep win at Roland Garros And it wasn't going her way against 90th-ranked Anna Karolina Schmiedlova. Hide Caption 2 of 9 Photos: Osaka, Halep win at Roland Garros Osaka lost the first set 6-0, so an upset was a possibility. Hide Caption 3 of 9 Photos: Osaka, Halep win at Roland Garros Schmiedlova, who had lost her last nine slam matches, couldn't miss while Osaka struggled. Hide Caption 4 of 9 Photos: Osaka, Halep win at Roland Garros But Osaka turned it around to win in three sets on a wet and windy day in Paris. Hide Caption 5 of 9 Photos: Osaka, Halep win at Roland Garros Also progressing was last year's winner Simona Halep, who needed three sets to beat Ajla Tomljanovic. Hide Caption 6 of 9 Photos: Osaka, Halep win at Roland Garros Jelena Ostapenko, the 2017 winner, fell in straight sets to Victoria Azarenka, hitting 17 double faults. Hide Caption 7 of 9 Photos: Osaka, Halep win at Roland Garros Azarenka -- the twice grand slam winner -- next faces Osaka in round two. Hide Caption 8 of 9 Photos: Osaka, Halep win at Roland Garros Alexander Zverev, the fifth seed, won three five-set matches last year in Paris. He won another five-setter Tuesday over John Millman. Hide Caption 9 of 9

Asked why the nerves remained throughout on center court, Osaka responded: "Logical reasons, first time playing a grand slam as No. 1. Won the last two, so I kind of want to win this one really bad.

"I have never played on Chatrier (court) before. This was my first time.

"And, yeah, I kind of feel like I'm having the thought of wanting to prove myself again."

Osaka will know she will need to raise her level in the second round when meeting fellow twice grand slam winner Victoria Azarenka, who downed struggling 2017 French Open champion Jelena Ostapenko 6-4 7-6 (7-4) in a match-up that certainly stood out at Thursday's draw.

Chasing history

If Osaka does go on to win the title in just under two weeks, she would become the first female player to win three straight majors since her idol Serena Williams in 2015.

You have to go back to 1988 and Steffi Graf for the last player to win all four in a single season.

Yet that all seemed in the distance when Osaka toiled against Schmiedlova, who didn't appear to be a threat to her more illustrious opponent.

Schmiedlova entered this fortnight on a nine-match losing streak in majors and had fallen at the first hurdle at Roland Garros on her past three visits.

That said, Osaka entered the French Open on the back of thumb and abdominal injuries, still posting a 7-1 record in the buildup on the surface she continues to adapt to.

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"Today was completely fine," Osaka said, referring to the thumb issue. "I didn't feel anything. Probably looked like I felt something, but, no, it was fine today."

The first set lasted 20 minutes and saw Osaka commit 13 unforced errors in the difficult Parisian conditions. When Osaka raced to a 3-0 lead in the second, thoughts of Williams' opener might have sprung to mind.

The record 23-time grand slam winner lost her first set 6-2 to Vitalia Diatchenko Monday before proceeding to crush her Russian rival 6-1 6-0.

Rain intervened

Rain, however, stopped Osaka's momentum and forced the players off court.

Upon the resumption, Schmiedlova won three games in a row to level at 3-3, turning the second set into a deep struggle.

Schmiedlova led 5-4 and 6-5, with Osaka two points from defeat in that 12th game four times.

"It's not easy to win against the No. 1," said Schmiedlova, whose ranking slipped to near 300th in 2017 from a career-best of 26th two years earlier. "I guess I felt it, and I didn't make it to the finish. It's not easy for my head and to beat her."

Osaka -- who overcame Williams and Petra Kvitova in her two dramatic grand slam finals -- broke and this time when holding a 4-1 edge in the tiebreak didn't let Schmiedlova back in it.

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An early break in the decider seemed to settle Osaka and she ended the encounter by landing the last 10 points. Following Osaka on Chatrier, defending champion Simona Halep also needed three sets to see off Australia's Ajla Tomljanovic 6-2 3-6 6-1.

Halep began last year's event by going the distance against Alison Riske, then only surrendered one more set en route to the final.

Ostapenko's double faults

While Osaka kicked on after winning in New York last year, the same couldn't be said of Jelena Ostapenko after her surprising title run in Paris that included blasting past Halep in the finale.

Hitting 17 double faults against Azarenka helped to undo a 4-3 break advantage in the first set and 4-2 lead in the second, when the Latvian later had to save two match points prior to being broken at 6-5.

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"The opponent for the first round was, I think, one of the toughest in the draw," Ostapenko, also defeated in the first round in 2018, said in her brief English press conference. "And I think I was rushing too much. And also conditions were very tough. It was super windy today."

It was also tough -- make that tough again -- for fifth seed Alexander Zverev at a grand slam.

Winning the year-end ATP Finals in London in November by defeating the legendary duo of Roger Federer and Novak Djokovic on back to back days, the German is nonetheless still seeking his big breakthrough at a grand slam.

He did make the quarterfinals at Roland Garros a year ago -- needing to post a trio of five-set comebacks -- and had to go five sets again Tuesday against tenacious Australian John Millman, 7-6 (7-4) 6-3 2-6 6-7 (5-7) 6-3.

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Playing four hours in the first round might not bode well for the rest of the fortnight, although the 22-year-old was still keen to remind reporters he was doing just fine this season despite dropping from third in the rankings.

"Everybody keeps on saying I had a tough year," said the matter-of-fact Zverev. "I mean, I'm still No. 5 in the world. Any of you guys know what I am in the race to London? I'm top 10.

"So it's not that bad, to be honest."