Karolina Pliskova and Elina Svitolina, who both had career-highlight victories over Serena Williams last season, are already through to the Brisbane International quarterfinals.
A 16-year-old high school student, who was inspired to take up tennis when she was 5 after watching Williams on TV, also made a mark on Tuesday with a first-round win.
Australian qualifier Destanee Aiava became the first player born in the 2000s to win a main draw match in an elite WTA event when she beat 31-year-old Bethanie Mattek-Sands 2-6, 6-3, 6-4 in a first-round match that spanned two days. She already has a wild-card entry to the Australian Open but, before then, will face two-time major winner Svetlana Kuznetsova in the second round of the tuneup event for the season's first Grand Slam.
The third-seeded Pliskova, who beat Serena Williams in the U.S. Open semifinals last year before losing the championship match to Angelique Kerber, beat American qualifier Asia Muhammad 6-1, 6-4 to secure the first spot in the quarterfinals. She earned five service breaks and was relatively untroubled in her second-round match.
The sixth-seeded Svitolina, the only woman to beat both Williams and Kerber in 2016, advanced with a 7-5, 2-6, 7-5 win over Shelby Rogers. She could meet the top-ranked Kerber in the quarterfinals.
In other second-round matches, Alize Cornet beat Christina McHale 6-2, 6-1, and No. 4-seeded Garbine Muguruza was playing a night match.
Aiava, who was born on May 10, 2000, and was No. 386 in the latest rankings, is still gathering experience.
"Pretty crazy," Aiava said of her first trip to the locker rooms in the main draw. "I walk in, and there is people I have watched on TV before and it's, like, 'Oh!'"
Aiava grew up in Australia to parents of Samoan heritage. Her mother, Rosie, has been her coach since she showed interest in the game. She keeps the teenager grounded.
After her milestone win, Aiava said her mother just said "good job" and took her back onto the practice courts for 20 minutes to work on her serve.
In men's first-round matches, sixth-seeded Lucas Pouille had a 7-6 (6), 7-6 (4) win over Gilles Simon, Viktor Troicki beat Japanese qualifier Yoshihito Nishioka 6-4, 7-5, and Jared Donaldson had a 6-4, 6-4 win over Gilles Muller.
Rafael Nadal, a 14-time major winner, was due to make his Brisbane International debut later Tuesday against Alexandr Dolgopolov.