Tearful US Open champion Naomi Osaka blamed tiredness after a surprise defeat in straight sets by Karolina Pliskova in the Pan Pacific Open final.
Japan's Osaka was hoping to give home fans a victory to celebrate in Tokyo but went down 6-4 6-4 to the Czech.
"I've literally never felt more tired in my entire life," said the 20-year-old, who plans to take some time off.
Former world number one Pliskova, the fourth seed, ended Osaka's 10-match winning streak in just 63 minutes.
"Naomi was maybe a little bit tired, you could see that. But the future is bright for her and congrats to her for an incredible few weeks," said Pliskova, 26, after her 11th career title.