– Now comes the match that Serena Williams didn't want to play.

As she plows forward toward a fourth consecutive U.S. Open title and a calendar year Grand Slam, Williams runs into the player whom she considers to be the best in the tournament in the quarterfinals Tuesday night, the one player who might have the best shot at beating the No. 1 player in the world.

That would be her sister, Venus.

"For me, I'm playing the best player in the tournament, and that's never easy," Serena said. "She's beaten me so many times. I've taken a lot of losses off her, more than anybody. She knows how to win, knows how to beat me, and knows my weaknesses better than anyone."

This will be the 27th time the sisters have played each other. That figure is extraordinary not only because they are the most successful sister-sister act in the history of sport, but they are also the oldest players in the women's draw. Venus is 35; Serena will be 34 this month.

Venus' road to the quarterfinal has been considerably more difficult than Serena's, starting with a first-round match against Monica Puig that went three sets and took 2 hours, 40 minutes. She also defeated rising Swiss star Belinda Bencic, a convincing two-set victory that seemed to prove she was at the top of her game, as well as being at the top of her age bracket.