Serena Williams beat her friend Caroline Wozniacki in head-to-head quarter finals game at Rogers Cup 2014 in Montreal. With that, the American player quelled the viral illness queries behind her to advance into the Rogers Cup semi finals. When it comes to tennis, Serena Williams and Caroline Wozniacki decided to put friendship behind them as they race for the championship title.

In a thrilling three setter, Serena Williams, 32, defeated the danish Caroline Wozniacki, 24, 4-6, 7-5, 7-5. Like Maria Sharapova, Caroline Wozniacki will head to Cincinnati to continue working on her game on the hard courts in preparations for the U.S. Open happening in late August.

Serena Williams, who has been plagued with the mysterious viral illness, stepped up to the challenge at Rogers Cup in Montreal. Caroline Wozniacki, just three months after breaking up with her fiancé Rory McIlroy, bonded with Serena earlier this summer, going to basketball games and enjoying beach time with the American all-time champion.

Despite having just come from winning a WTA title in Istanbul, Caroline Wozniacki didn’t have the edge over Serena Williams to advance into the semi finals of Rogers Cup 2014.

Maybe the Danish star’s stamina was spent from training for the New York City Marathon come his fall. Caroline Wozniacki signed up to run the course to raise money for children.

Serena Williams will never run the marathon though. In the latest press conference, the 32-year-old tennis player scoffed at the idea of running the marathon.

Caroline Wozniacki is one of the few athletes, who accepted the challenge of running a marathon at the peak of her career.