Simona Halep will ascend to No. 2 when the updated WTA rankings come out Monday. But it's No. 5 Caroline Wozniacki that could have the most momentum heading into next month's French Open.

SI.com reported that Wozniacki defeated Halep 7-5, 5-7, 6-2 in the semifinals of the Porsche Tennis Grand Prix in Stuttgart, Germany and will face Angelique Kerber in Sunday's finals.

Caroline Wozniacki hires Arantxa Sanchez-Vicario for the clay-court season

Wozniacki has one minor tournament victory in 2015, but had not built upon the promising conclusion of her 2014 season until Saturday. According to SI.com, the Dane simply took the legs out of the Romanian by making her run all over the court for 2 hours, 58 minutes.

Wozniacki trained for and ran the New York Marathon last year and one of the fittest players on the tour. But she had not been able to take advantage of her fitness much this season.

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She took full advantage against Halep.

"I came out strong there and just tried to keep it going," Wozniacki said after the match. "I knew I had loads of energy left for the third set. That's what I was going for, to try to stay longer in the rallies, make her run, and stay aggressive, and that's really what I did."

Credit Wozniacki for hiring Arantxa Sanchez-Vicario, a four-time Grand Slam champion and clay-court specialist to help her with her clay-court game. Wozniacki won exactly one match last year on clay and already has three wins on the surface in Stuttgart.

Credit Sanchez-Vicario for seemingly having an immediate impact on Wozniacki's game, which should be a good match for clay because of her fitness.

Wozniacki played so well that Halep said after the match she wasn't disappointed in her own game.

"I'm smiling because I had a good match. I think I played good tennis, but she was just better than me," said Halep, according to SI.com. "She was running a lot and she was fighting until the end - she was stronger. So I'm happy with this match. I'll only take the positive things and look forward from here."

The bigger question is whether Wozniacki can complete her Stuttgart run and whether she will return to her late 2014 form where she arguably was the second best player in the world behind Serena Williams.

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