Japan's Naomi Osaka kept her fine run at the BNP Paribas Open alive on Wednesday, beating fifth seed Karolina Pliskova of the Czech Republic in straight sets in the singles quarterfinals.

The 20-year-old Japanese, plowed through the 6-2, 6-3 upset in 1 hour, 18 minutes to earn a meeting with top seed and world No. 1 Simona Halep of Romania in the semifinals, Osaka's first in a Premier Mandatory event.

In what was expected to be a slugfest at Indian Wells Tennis Garden, the 44th-ranked Osaka piled pressure on Pliskova, causing trouble from the baseline and forcing her opponent into uncharacteristic errors.

But despite winning 73 percent of her first serves, Osaka said it was her service return that was key. The Japanese won six of 10 break points in the match while Pliskova could only convert two of four.

"I don't really think I served that good to be honest. I think I returned well," she said. "(Pliskova) is one of the best servers on tour and I was able to break her quite a few times, so I'm quite happy about that."

Pliskova, who more than canceled out her five aces with six double faults, got off to a shaky start in the first set, committing three errors in the opening six points, including a double fault on break point.

She got on track to win the third game, but Osaka kept the intensity up over the rest of the set, capitalizing on Pliskova's 11 unforced errors and anticipating the Czech's movement to bang home multiple running crosscourt forehand winners.

Pliskova took advantage of a second-set lull from Osaka, changing tactics and showcasing her strong serve with heavy blows down the center that allowed her to take a 3-2 lead.

(Getty/Kyodo)

But that was as good as it got as Osaka drew even in the next game and ran away with the next three for the win.

Osaka advances to the semifinals of a WTA event for the first time since the 2016 Pan Pacific Open in Tokyo, where she lost to Denmark's Caroline Wozniacki in the final. The win makes her the first Japanese to reach the semifinal of a Premier Mandatory event.

"I'm really happy I'm able to win matches now," said Osaka. "So I feel really good and I want to thank everyone for cheering for me."

"I just try to focus on one match a time. I'm not really thinking too much about who I'm playing, so that's been working out for me."

Osaka upset former world No. 1 Maria Sharapova of Russia in the first round before going on to beat Poland's 32nd-ranked Agnieszka Radwanska, American Sachia Vickery, and Maria Sakkari of Greece.

She faces Halep in the semifinal on Friday, looking for her first win in her fourth meeting with the two-time Grand Slam finalist.