SINGAPORE: Garbine Muguruza continued her dream debut at the WTA Finals by completing round robin play with a perfect 3-0 record to advance to the semi-finals after a hard fought 6-4 4-6 7-5 victory over Petra Kvitova on Friday.

By topping the White Group, the Spaniard set up a showdown against Poland's Agnieszka Radwanska while Kvitova (1-2) will be banking on her already eliminated Czech Fed Cup team mate Lucie Safarova (0-2) to beat Angelique Kerber to help her advance.

Germany's Kerber (1-1) only needs to secure a set in Friday's second match to book a last four berth against Red Group winner Maria Sharapova but Muguruza was spared the agony of relying on others by claiming a third straight triumph.

"It's amazing to reach the semi-finals," Wimbledon finalist Muguruza said in a courtside interview. "To be here is a great payoff for an amazing year and hopefully I can continue winning and playing like this."

The right-handed Spaniard had grown accustomed to receiving left-handed serves in a group containing a trio of southpaws and immediately forged three break points in the opening game that Kvitova did well to survive unscathed.

The reprieve was short-lived, however, and Muguruza edged ahead when the pair traded three consecutive breaks in the middle of the set and the recent China Open winner raced through the eighth game to move 5-3 up.

Kvitova sent down back-to-back aces to ensure Muguruza would need to serve for the set and the world number three forced the Czech into a return error to claim the set 6-4 and ensure she would at least advance from the pool as a top-two finisher.

The second set turned into a war of attrition as both players coughed up point after point on their fragile second serves to exchange six breaks in the first seven games before Muguruza ended the sequence to hold in the eighth.

The 22-year-old dropped her racket and let out a yelp of pain when she turned her ankle in the ninth game and while her movement appeared unaffected, her choice of shot and accuracy faltered as she allowed Kvitova to level with another break.

Both players continued to struggle on serve in the decider as the pair racked up a match total of 15 combined breaks between them, the last arriving in the 11th game of the set when Muguruza moved 6-5 ahead on Kvitova's backhand error.

Despite finally gaining an advantage, Muguruza needed to dig deep to prevent the contest from going to a third set tiebreak, maintaining her composure as Kvitova staved off three match points to seal the contest on her fourth with a backhand volley.

"It was crazy right, oh my gosh," Muguruza added.

"Petra is an amazing player and she was obviously playing great. I was so nervous and she made sure I had to concentrate and give it my best and I can't be happier with this ending."