The 25-year-old Estonian has won 28 of her last 30 matches, including her title run at Ostrava. Prior to that stretch she had a 19-13 record for the year.
"I've really been enjoying being on court, just having a good time. I think that's been the main thing why I've been doing so well. I do feel like I can take on everyone,'' Kontaveit said.
Kontaveit, who soared from No. 30 in the rankings into the top 10 since she started working with Dimitry Tursunov at the Cincinnati Masters, clinched a spot in the tournament´s final four.
"I think each win towards the end of the year just gave me a little bit of more confidence," Kontaveit said. "The balls just started rolling.''
In the late match Friday, Garbine Muguruza rallied to beat Barbora Krejcikova 2-6, 6-3, 6-4, to remain in contention for the title. To qualify for the semifinals for the second time in her career, the Spaniard (1-1) needs a win on Sunday against Kontaveit (2-0) and a Krejcikova victory over Pliskova (1-1).
Krejcikova, the French Open champion, is not eliminated at 0-2, but needs to beat Pliskova in two sets and a Muguruza loss.
The second-seeded Krejcikova broke Muguruza's service in the fifth and seventh games to take the first set in just 36 minutes. But Muguruza came back and broke Krejcikova in the fourth game to take a 3-1 lead and added a break in the eighth game.
"I am very happy about my fighting spirit today, I lost the first match in a tough way and won this one in a tough way,'' Muguruza said. "I'm very happy in the way I handled difficulties.''
Muguruza, who is a local favorite after winning titles in Monterrey in 2018 and 2019, had a break in the third game of the third set and held on for the win.
"The crowd really helped me today, I said it before, and I mean it, they cheer me up and I said I'm not leaving this court before changing things around," she added.
In doubles, the second seeded team of Shuko Aoyama and Ena Shibihara defeated Nicole Melichar-Martinez and Demi Schuurs 6-4, 7-6 (5). The Japanese pair qualified for the semifinals when No. 7 seeds Darija Jurak and Andreja Klepac triumphed 6-7 (10), 7-6 (4), 10-5 in a nearly 2-hour match against No. 5 seeds Samantha Stosur and Zhang Shuai.
The tournament was canceled last year because of the COVID-19 pandemic. The WTA Finals are being played in Guadalajara for this year only, with the event scheduled to return in 2022 to Shenzhen, China.