Naomi Osaka's Wimbledon preparations received a setback when she retired at the start of the second set in Saturday's Bad Homburg final because of a foot injury. 

The fourth-seeded Japanese player, in her first grass-court final, was trailing 6-1 1-0 to Karolina Muchova of the Czech Republic when she pulled out.

Osaka had taken a medical timeout in the first set. Then, after gesturing she could not continue, she walked over to shake hands with Muchova and the umpire.

"I just want to say thank you to everyone who came to watch the match," Osaka told the crowd during the trophy ceremony.

"I apologise for not being able to finish, but this atmosphere was incredible the whole week."

A four-time Grand Slam champion, the 28-year-old Osaka has never been beyond the third round at Wimbledon, which begins on Monday.

Seeded No 14, she is scheduled to play Elsa Jacquemot in the first round.

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