Way back then the sisters were on the same level in terms of individual achievement, but the gap eventually grew unbridgeable: Serena has become perhaps the greatest singles player of the Open era, with 23 Grand Slam singles titles and unprecedented late-career success.

It is Serena who holds the edge in all significant categories and who was ranked No. 1 for 316 weeks to Venus’s 11. Serena also leads the head-to-head rivalry, 17-12, and has won 10 of their 15 Grand Slam matches, including their most recent meeting in a major tournament, at the 2017 Australian Open. That day, Serena prevailed in the final despite being two months pregnant, and with Venus one of the select few aware of the circumstances.

“It was two against one,” Venus recalled on Wednesday night. “At least this time it will be fair.”

But tennis, like life, can run in cycles, and for the moment the Williams sisters are back on what looks more like equal footing, with Venus seeded 16th and Serena 17th.

At age 38, Venus has struggled to match her stellar results from 2017, but she had two quality victories in her opening rounds this week — defeating the former U.S. Open champion Svetlana Kuznetsova in three sets and the explosive Camila Giorgi in two. At age 36, Serena reached the Wimbledon final last month, but she is still searching for consistent form and her equilibrium a year after giving birth to her daughter, Olympia.