Serena Williams defeated her older sister Venus Williams in three sets, 3-6, 6-3, 6-4, in the second round of the Top Seed Open in Lexington, Kentucky on Thursday. The Williams sisters met for the 31st time in their historic rivalry that spans over two decades. It had been two years since the sisters' last meeting in the third round of the 2018 US Open. Thursday's match may very well be the last time that the two face each other on tour. Venus turned 40 years old this past June and Serena will turn 39 in September.

"I think she played unbelievable," Serena said of his elder sister in the postgame, on-court interview. "She's doing so good. I honestly don't know how I was able to pull it out in the end. She fought well."

In the first set, thanks to solid serving from Venus, she won six of the last seven games to take the early lead in the match. But, the first set win for Venus didn't translate to a win, which has often been the case in the Williams sisters rivalry. Entering the match, the winner of the first set had won all but four encounters. Serena forced a third set, and rallied from a break down, winning four straight games and overcoming a 2-4 deficit to seal her victory over Venus. Serena now owns the 19-12 advantage in the rivalry, and has won ten out of the last 12 meetings. Serena recorded 16 aces to six double faults, while Venus notched six aces to 11 double faults.

Venus is ranked No. 67 in the world and the oldest player in the top 400 of the current WTA rankings. In 2011, Venus was diagnosed with an autoimmune disorder that causes fatigue and joint pain. Serena is ranked No. 9 in the world but has yet to win a Grand Slam singles title since winning the 2017 Australian Open (against Venus in the final). She's 0-4 last four Grand Slam finals; 2018 US Open, 2018, 2019 Wimbledon, 2019 US Open. Serena currently has 23 career Grand Slam titles and is one away from tying Margaret Court's all-time record of 24 Grand Slams.

While in recent years, the rivalry has become lopsided in Serena's favor, each time the pair has taken the court, the champion sisters still represented each others' fiercest challengers.