With a chance to make a statement in the WTA Finals, Muguruza couldn’t overcome a better-rested opponent on Saturday. She will not make the season-ending tournament’s final match.

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“I was obviously tired,” said Muguruza, who was also in the doubles semifinals. “I think Aga played very good today.”

The victor: Agnieszka Radwanska of Poland, who will be in the title match for the first time in seven appearances. She defeated Muguruza, the eight-woman competition’s top remaining seed, 6-7 (5), 6-3, 7-5.

“I have no words to say really,” Radwanska said in her courtside interview. “I didn’t know if I could come back after that first set, but I think it was a great match from the beginning until the end, so many rallies and a lot of running. I’m just so glad I could win this match in the end.

“After two losses in the beginning I thought it was kind of over for me here.”

Fifth-seeded Radwanska, the fifth seed, reached the semifinals in 2012 and 2014.

Her opponent: Petra Kvitova of the Czech Republic, seeking her second WTA Finals title. Kvitova eliminated Maria Sharapova 6-3, 7-6 (3) in Saturday’s other match.

Radwanska and Kvitova play for the title on Sunday in Singapore. Both players knocked out opponents who were 3-0 in round-robin play; both players were 1-2 in the preliminary stage.

Kvitova won six of her eight matches against Radwanska, including one this year.

“I didn’t really expect to be in the semis after the first losses and now it’s the final,” Radwanska said.

So both finalists are surprised.

“I didn’t expect this, for sure,” Kvitova said. “I had two losses in my group, and I couldn’t really believe I would play the semifinals. And I knew Maria would be strong today — she played so well in the round robin group, so I expected a really tough match.

“But I knew I had the game to beat her, and that I really had to keep trying today.”

Kvitova benefits from much career success, including Wimbledon titles in 2011 and 2014. She won the WTA Finals in 2011.

Muguruza’s consolation: She and Carla Suarez Navarro will face Martina Hingis and Sania Mizra in Sunday’s doubles final.

Contributing: WTA, Associated Press