World number one Garbine Muguruza lost 6-2 6-0 to Caroline Wozniacki in the Pan Pacific Open semi-finals in Tokyo.
Spain’s Muguruza, playing her first tournament since moving to the top of the rankings, was beaten in one hour by the Danish third seed.
“I felt my energy was a little bit low and I didn’t make the important shots,” Muguruza said. “I’m very disappointed.”
In the other semi-final, Anastasia Pavlyuchenkova beat seventh seed Angelique Kerber 6-0 6-7 (4-7) 6-4.
Kerber lost the first eight games of the match in Tokyo and was 5-2 down in the second set.
But the German took the second set on a tie-break and raced into a 3-0 lead in the decider.
Russian world number 23 Pavlyuchenkova, though, recovered and achieved the decisive break in the seventh game before sealing victory and a place in Sunday’s final.