Madrid Open: 'More comfortable' on clay courts, says Naomi Osaka

Naomi Osaka eased concerns about her form and fitness by coming through a tricky first round against Dominika Cibulkova on Sunday at the Madrid Open, declaring she's "more comfortable" on clay courts than in the past.

Osaka has struggled since splitting with her coach Sascha Bajin in February while an abdominal injury forced her to withdraw in Stuttgart eight days ago, creating doubts about her challenge at the French Open later this month.

But there was little sign of physical problems during a testing 6-2, 7-6 (8/6) victory over Cibulkova and afterwards, Osaka said: "I feel good. I don't have much pain in my abs so that's always a good sign." The Japanese world number one will now face Spain's Sara Sorribes Tormo in round two.

Osaka looked set for a more comfortable passage after a dominant opening set but she was stretched by the battling Cibulkova in the second.

By the end, Osaka had hit 43 winners and eight aces while world 33 Cibulkova conjured up 23 winners.

"I was also kind of thinking, like, there is nowhere else I'd rather be and honestly I train for these moments so I have to give it 100 percent," said Osaka after her first main draw win in Madrid.

"I feel like there's an adjustment period for me on clay and it took a few years.

"But now I'm more comfortable. I'm not sure if it's because I had a really long training block before I came to start the season, but yeah, it feels good." Osaka's pair of Grand Slam successes have come on hard, at the US and Australian Opens, but she is yet to find her best on clay.

If the abdominal injury has healed, Osaka can feel encouraged by her performance against Cibulkova, one of the tour's gutsiest competitors even if the Slovakian is also enduring a difficult start to 2019.

Pliskova saves four match points

Meanwhile, French Open champion and two-time Madrid winner Simona Halep brushed past Russian qualifier Margarita Gasparyan 6-0, 6-4.

"It was a good match, even if the first set was fast. The second one was tougher, and I feel happy that I could win this match," said third-seeded Halep.

Former world number one Caroline Woznacki's Madrid Open lasted just minutes when she retired at 0-3 down to France's Alize Cornet suffering with a back injury.

Wozniacki, the 2018 Australian Open champion, has been battling rheumatoid arthritis in recent months.

"I don't consider it like a real win over Caroline," Cornet said.

Fourth seed Karolina Pliskova saved four match points to see off highly-rated Ukrainian teenager Dayana Yastremska 5-7, 7-6 (7/5), 6-3.

Unseeded Pauline Parmentier of France defeated Ukrainian sixth seed Elina Svitolina, who had been struggling with a knee injury, 6-4, 7-6 (8/6).

US 13th seed Madison Keys was also a surprise first round loser, going down 3-6, 6-4, 6-1 to Sorana Cirstea of Romania.

However, there were no such problems for former US Open champion -- and recently engaged -- Sloane Stephens as the eighth seed defeated Polona Hercog of Slovenia 6-2, 7-6 (7/4).

Stephens, who announced her engagement to US football international Jozy Altidore last week, goes on to face former world number one Victoria Azarenka.

Only two ATP matches were played on Sunday. Australia's Nick Kyrgios was a 7-6 (7/4), 6-4 loser to Germany's Jan-Lennard Struff, a quarter-finalist in Barcelona last month.

Felix Auger-Aliassime, just 18, won the all-Canadian battle with Denis Shapovalov 6-2, 7-6 (9/7) to set-up a second round clash against world number two Rafael Nadal.