Serena Williams has raised eyebrows after her name was added to the International Tennis Integrity Agency’s latest International Registered Testing Pool list more than three years after she retired from professional tennis. Players cannot compete without entering the pool, and past competitors who have returned from retirement must sign up to make themselves available for out-of-competition testing at least six months prior to making a comeback.
Caroline Wozniacki, a former world No. 1 and one of Williams’ good friends, did the same when she returned to competition in 2023, having retired at the 2020 Australian Open. And Williams’ appearance on the ITIA’s testing pool has sparked speculation over a potential comeback.
The 44-year-old ended her career on home soil at the 2022 US Open, upsetting second seed Anett Kontaveit before bowing out in the third round. Since retiring, Williams has still made time for tennis, sometimes taking to social media to share snaps of herself on the court.
Williams’ older sister, Venus, is also still active on the tour. Venus returned from a 16-month hiatus at the Washington Open over the summer and also competed at the Cincinnati Open and US Open. In Flushing Meadows, she reached the doubles quarter-finals with Leylah Fernandez. And she’s set to compete in the ASB Classic in Auckland next month.
Now, fans are wondering whether Williams will join her sister on the professional tennis circuit, be it on the singles tour or to revive their successful doubles partnership. The 23-time Grand Slam champion’s name appeared on the ITIA’s latest testing pool list, published on October 6, 2025.
Players on the registered list are required to comply with ‘whereabouts’ testing – informing the ITIA of their whereabouts for a one-hour slot every day via the ADAMS platform. This allows the ITIA to conduct random, out-of-competition doping tests.
Williams currently remains on the ITIA’s ‘retired’ players list. The organisation states that retired players “may not return to sanctioned events unless they have made themselves available for out-of-competition testing for at least six months prior to the event in question”.
If the former world No. 1 is considering a comeback, then she’s taken the first step to be eligible for competition from mid-2026 onwards. Wozniacki went through a similar process before her comeback in 2023.
The Danish tennis star was not reinstated by the ITIA until August of that year – one week before she retired at the Canadian Open – but had re-entered the testing pool more than six months earlier.
Williams’ reason for rejoining the testing pool is still not known, but one of her old coaches, Rick Macci, had tipped the 44-year-old to team up with Venus at this year’s US Open. That never came to fruition, but Williams would be eligible to compete in Flushing Meadows in 2026 if she remains in the pool.
“Asked if Serena will play doubles with Vee at the OPEN. My gut is probably because at the end of the day Serena can still play even though she has been away. Her serve is still one of the best on the planet and when she competes her mindset is like granite,” he tweeted.
Venus herself also shared her wish to see her sister back on tour after making a comeback in July, and said they still hit together often. “I mean, I keep saying to my team, ‘The only thing that would make this better is if she was here’, like we always did everything together, so of course I miss her. But if she comes back, I’m sure she’ll let y’all know,” she said.