Garbine Muguruza, of Spain, celebrates after defeating Paula Badosa, of Spain, during a semifinal match at the WTA Finals tennis tournament in Guadalajara, Mexico on Nov 16, 2021. (REFUGIO RUIZ / APF)

Garbine Muguruza saw off fellow Spaniard Paula Badosa 6-3 6-3 and Anett Kontaveit outlasted Maria Sakkari 6-1 3-6 6-3 to punch their tickets on Tuesday to the WTA Finals championship match in Guadalajara.

In their first career meeting, Muguruza's superior firepower put Badosa on the back foot from the outset and she broke the Indian Wells champion for a second time with a forehand winner to take the first set.

I think it's the best match that I played so far here in Guadalajara ... It was a tough match facing another Spaniard (Paula Badosa) in the semi-finals ... so it was tricky. But I'm very happy that I got the win.

Garbine Muguruza, Spanish professional tennis player

Badosa's frustration boiled over during the change over and she was unable to hold serve in the lengthy second game of the second set, giving the former world number one another early break on the sun-drenched court.

Muguruza fended off Badosa's three break point chances in an 11-minute third game to take a 3-0 lead and rolled on from there, firing an ace to go up 5-2 and sealing the win when Badosa hit a backhand into the net on match point.

"I think it's the best match that I played so far here in Guadalajara," Muguruza said.

"It was a tough match facing another Spaniard in the semi-finals ... so it was tricky. But I'm very happy that I got the win."

The loss ends a breakthrough year for Badosa, who will finish the season at a career-best world number eight.

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Paula Badosa, of Spain, reacts during a semifinal match Against Garbine Muguruza, of Spain, at the WTA Finals tennis tournament in Guadalajara, Mexico on Nov 16, 2021. (REFUGIO RUIZ / AP)

Garbine Muguruza will have her work cut out for her when she faces the red-hot Anett Kontaveit, who played flawless tennis to take the first set off Maria Sakkari in less than 30 minutes under the lights in the high-altitude Mexican city

"Today was a tough day," Badosa said.

"I didn't feel myself. I didn't play the match that I was expecting."

Muguruza will have her work cut out for her when she faces the red-hot Kontaveit, who played flawless tennis to take the first set off Sakkari in less than 30 minutes under the lights in the high-altitude Mexican city.

Sakkari, who emerged the victor of a draining match the night before against Aryna Sabalenka, finally broke the Estonian's serve in the second set to force a decider, much to the delight of the fired up crowd.

The match ultimately hinged on a lengthy Sakkari service game with the Greek trailing 3-4 in third.

On break point, Sakkari pounced on a blocked service return but rifled her forehand into the net to give Kontaveit a 5-3 lead she would not relinquish.

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Two-time Grand Slam champion Muguruza is making her fourth appearance at the season-ending finals and her first in the championship match, while the eighth-seeded Kontaveit will be playing in the biggest match of her career on Wednesday.