Serena Williams has finally met her match.
The 23-time Grand Slam singles champion is the finest female player of her era (let's face it, of all time) and has been so far ahead of the pack for years that eclipsing Margaret Court's 24 major titles has always seemed a matter of when, not if.
That gap to the rest has narrowed in recent years, but at 38, and having stepped away from the sport to give birth in 2017, she is still right at the top of women's tennis, reaching four of the last seven major finals.
So with Wimbledon cancelled due to the coronavirus, and the traditional tennis schedule on hold for the foreseeable future, Williams has enlisted the help of an unusual training partner.
Perhaps the only person who would go into a match against Williams confident of giving her a run for her money: Herself.
"You're tough," she says at the end of a rally, dressed in one of her US Open outfits.
Her 'opponent', in Williams' 2016 Wimbledon gear, replies: "You're not so bad yourself."
Those SW19 lawns could do with a mow, mind.
