Madrid, Spain: 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.
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 will now face the winner of an all-Spanish tie between Lara Arruabarrena and 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 to her opponent's 23.
The world number one'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.
Osaka dropped serve in the third game but immediately hit back, a ripped backhand return too good for Cilbulkova to retrieve.
Cibulkova played deep behind the baseline, allowing her opponent time to dictate as Osaka won five consecutive games to claim the set.
The second began like the first, with Cibulkova breaking early and she held the advantage until 4-3, only for a fourth double fault to allow Osaka back in.
Three well-executed drop-shots from Cibulkova squared the set at 5-5 and an irritated Osaka, whacking her racket against her foot, was taken to a tie-break.
But frustration seemed to invigorate Osaka, who pulled 5-2 clear after a superb backhand winner. Cibulkova fought back to 5-5 and then saved a match point, on Osaka's serve, to level again.
A big serve gave Osaka another chance and this time she took it, as Cilbulkova went long to leave her relieved opponent pumping her first after an hour and 55 minutes.