World number one Garbine Muguruza has lost in the semi-finals of the Pan Pacific Open to defending champion Caroline Wozniacki.

The Spaniard, who was playing her first tournament since moving to the top of the world rankings, was comprehensively beaten 6-2 6-0 by her Danish opponent.

The 23-year-old conceded she struggled to find her best form throughout the contest, blaming a lack of energy for her lacklustre display.

"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, seventh seed Angelique Kerber, still chasing her first WTA Tour success of the season, was beaten by Russia's Anastasia Pavlyuchenkova 6-0 6-7 (4-7) 6-4.

Kerber looked in danger of being humiliated during the contest, as she lost the opening eight games of the match in Tokyo, but she rallied and moved into a 3-0 lead during the decisive set, only to eventually lose out to the world number 23.

Muguruza and Kerber will now turn their attention to next week's Wuhan Open, while Wozniacki and Pavlyuchenkova will contest Sunday's final at the Ariake Coliseum.