Anett Kontaveit powered past third-seeded Karolina Pliskova 6-4, 6-0 to lead the way into the semi-finals of the season-ending WTA Finals at Guadalajara on Friday.
The eighth-seeded Estonian continued her late-season surge, notching her 12th straight WTA match win as she assured herself of finishing in the top two of her group in the round-robin phase.
Spain's Garbine Muguruza kept her hopes of advancing from the same group alive with a 2-6, 6-3, 6-4 victory over reigning French Open champion Barbora Krejcikova.
Kontaveit, whose win streak included titles at Moscow and Cluj-Napoca, had beaten Krejcikova in her tournament opener.
"Of course, very thrilled to be in the semi-finals," said Kontaveit, who needed just 57 minutes to roar past Pliskova, winning 24 of her 29 first-service points and claiming the last eight games for her first career victory over the Czech in four meetings.
"I wasn't thinking about the fact that I was three-love down in previous matches," Kontaveit said. "Every time you step on the court you have a new opportunity. The previous matches don't really matter. It's a new day and you have to beat the player you're playing against."
But Kontaveit is riding a wave of confidence, having won 28 of her past 30 matches.
"I've really been enjoying being on court, just having a good time," she said.
"I think that's been the main thing why I've been doing so well. I do feel like I can take on everyone. I never expect an easy match, I always expect it to be tough. I just try my best when I go out there."
Muguruza's gutsy victory over Krejcikova means that she along with Krejcikova and Pliskova remain in the hunt for a semi-final spot heading into their final round-robin matches on Sunday.
After holding serve just once in the opening set the Spaniard raised her level, breaking Krejcikova for 3-1 in the second and stretching her lead to 4-1 with a superb service effort that featured two aces in the fifth game.
Krejcikova managed to regain the break in a hard-fought seventh game, finally converting her sixth break of the game.
But Muguruza broke back and served out the set with an ace up the middle.
Muguruza battled to a break for a 2-1 lead in the third set -- taking the 12-minute game on her sixth break point -- and made the advantage stand up.
It was the fourth meeting of the season between the two. Muguruza had beaten the Czech in the Dubai final but lost to her at Cincinnati and the US Open.
The elite tournament was moved to Guadalajara this year from its usual home in Shenzhen, China, due to the coronavirus pandemic.