The 29-year-old came to the rescue after the 13-strong Aussie contingent's grass-court invasion began on a warm opening day with an injury-hit defeat for Aleksandar Vukic and a defeat for Roland Garros giant-killer Adam Walton.
Former quarter-finalist Kasatkina, the high-profile import who'd been the last Australian standing at Roland Garros, had entered her ninth Wimbledon on the back of a winless grass-court campaign, admitting she had no expectations of enjoying a deep run.
But though she reckoned she knew nothing about her Welsh opponent "except that's she's about 10 years younger than me - and that's enough", Kasatkina soon discovered after winning the first set comfortably that she'd have a fight on her hands on court 16.
The 18-year-old Mimi Xu hit back to take the second set before Kasatkina regrouped and controlled the decider for a 6-2 3-6 6-2 win in one hour 42 minutes, setting up a second-round clash with Janice Tjen, who last year became the first Indonesian woman in 23 years to win a tour title.
Earlier, Vukic had become the first casualty, suffering a knee injury before bowing out 7-6 (9-7) 6-1 6-1 to a familiar US foe Jenson Brooksby, who'd also defeated him in Eastbourne last week.
Vukic had been hoping for a decent run at the slam where he had the fortune -- and misfortune -- to play Carlos Alcaraz and Jannik Sinner in the past two years, knowing a run to the third round would likely earn him another crack at the Italian reigning champion after being filleted by him in straight-sets in 2025.
World No.104 Vukic had his chances in a tight opening set, racking up a couple of set points as he led 6-4 in the tiebreak, only for Brooksby to save the first with an audacious drop shot before prevailing on his fifth set point.
After an immediate break in the second set Brooksby, ranked 23 places higher than the Australian, really took control, with Vukic beginning to move less easily and he ended up needing a medicasl time-out after being outplayed in the second set, .
The American was not about to let Vukic off the hook, racing through the third set to earn victory in one hour 53 minutes, with the Sydneysider reporting afterwards: "It's an MCL strain, the same issue I had in the Birmingham tournament a few weeks ago but I don't think it's anything serious."
Walton, the Queenslander who'd enjoyed the best win of his career when knocking out former world No.1 Daniil Medvedev at the French Open, enjoyed an excellent start against Croatian Dino Prizmic, taking the first set but fell away after losing a second-set tiebreak, eventually succumbing 4-6 7-6 (7-3) 6-4 6-2.
