Garbine Muguruza tasted her first defeat as world No. 1 on Saturday, losing to defending champion Caroline Wozniacki in straight sets in the Toray Pan Pacific Open semifinals.

Wozniacki, who also won the tournament in 2010, needed only an hour to swiftly dismiss Muguruza 6-2, 6-0 in an unexpectedly one-sided affair at Ariake Colosseum, where the Dane will face Anastasia Pavlyuchenkova in Sunday's final.

Earlier, world No. 23 Pavlyuchenkova fended off a major fight back from two-time Grand Slam champion Angelique Kerber to win 6-0, 6-7(4), 6-4, reaching her first Pan Pacific Open final.

Muguruza was competing in her first event since topping the WTA rankings on Sept. 11. The Spaniard breezed through her first two matches at this tournament but as fate would have it, was eliminated by the same opponent who knocked her out in the last four three years ago.

Muguruza said former No. 1 Wozniacki, who is currently ranked sixth, was always going to be a tough test.

"No matter what ranking I am or Caroline is, in this type of match it doesn't matter because it's always going to be difficult," Muguruza said. "The ranking doesn't make me a favorite in the match; it was always going to be a battle. I don't feel like I should win every tournament I go to."

"Today, maybe my best tennis wasn't there. She played good and I'm not going to think a lot about this because in a few days I have more matches to come, so that's it."

Entered in two upcoming competitions in China and having qualified for next month's WTA Finals in Singapore, Muguruza had described the Pan Pacs as a "training tournament" for her.

Muguruza admitted the extra work she has been doing in the gym and on practice courts has taken a slight toll on her.

"I didn't feel that fresh," she said. "In the long rallies, I was struggling a little bit. I felt my energy was a little bit low, but I think she just had a good match. I didn't make the important shots in the important moments so the match went to her side very fast."

Wozniacki will appear in her fourth Pan Pacs final, having been runner-up in 2014. She has won at least one title every year since 2008, and is looking to extend that run on Sunday against Pavlyuchenkova.

"I think there are some tournaments where you just feel good and do well almost every year, and this is one of them," Wozniacki said. "After having a really tough match yesterday -- Dominica (Cibulkova) was playing really well and really aggressive -- I was kind of ready for that playing Garbine today."

"I'm just happy to be in the final again and I'll try to take it one step further."

In the first semifinal, Pavlyuchenkova admitted to thinking she had lost the match when she was down 3-0 in the final set.

"I was already thinking about going to Wuhan, when I should fly. In my head I was booking flights already," the Russian said, referring to the next tournament starting Sunday in China. "But at the same time, I always fight to the last moment, the last point."

In the opening set, Kerber was a stark contrast to herself from a day earlier, when she outlasted Karolina Pliskova in a quarterfinal pitting two former world No. 1s and also a rematch of last year's U.S. Open final.

Pavlyuchenkova flew through the first set in 19 minutes as Kerber appeared sluggish, able to win just 10 points, and it wasn't until the third game of the second set that Kerber finally won her first game of the match, breaking Pavlyuchenkova.

Kerber sought a medical timeout to receive treatment on her left forearm and the German returned to begin an impressive turnaround, going on to win the set in a tiebreak after being down by as much as 5-2.

Kerber won the first three games of the third set, but then Pavlyuchenkova returned the favor with a comeback of her own, rattling off the next five before connecting on the second match point to book her spot in the final.