When Kiki Bertens faces Serena Williams today in the U.S. Open, it will be the biggest match of her life.

The 23-year-old Dutch player, ranked 110th in the world, will try to grapple with the world's No. 1 player on the Arthur Ashe Stadium court in a second-round match.

Against Williams, Bertens will be going up against an all-time great with an all-time reserve of mental toughness. Bertens has made a point of watching Williams play, and cites her steely mentality as a weapon as big as her serve.

"I think mentally she's great; even when she's down, she's always fighting for every point," Bertens said. "She's really aggressive. I love to watch her play. I think her game is unbelievable, she is so aggressive. I think I can learn a lot from that because I'm trying to play aggressive, too."

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It's fairly safe to say that Williams has little firsthand knowledge of Bertens' game, having never played her. Nonetheless, "I think she's playing well," Williams said. "She does a lot of things well. She had a big serve. It's definitely something that I look forward to."

Bertens is 6 feet, and won a slugfest with Mirjana Lucic-Baroni, which at least gives her a taste of the power that Williams serves up.