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 world number one will now face Spain's Sara Sorribes Tormo in round two.
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 and four seed Karolina Pliskova saved five 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).
In one of the few ATP matches 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.