After main man de Minaur saw off potentially troublesome French veteran Adrian Mannarino 6-3 6-2 6-2 on Thursday morning, the 20-year-old former Aussie No.1 Joint took to the same court 3 with high hopes of building on her first-round victory over returning seven-time champ Williams.
But faced by another big crowd again screaming largely for her opponent, Joint this time saw another brilliant start slip tamely away as Alexandra Eala, a young heroine in the Philippines, roared back to defeat her 3-6 6-2 6-0.
The US-born Queenslander had grabbed headlines around the world for her defeat of 44-year-old Williams on Centre Court, eventually outstaying the legend who ended up struggling with the pace and physicality of the match.
But 21-year-old Eala, defeated by Joint in an epic final on the Eastbourne grass last year, proved a very different proposition, as she only got more dominant in the latter stages of her revenge mission, reeling off the final nine games to prevail in three minutes under two hours.
Joint, who had begun in the same exhilarating manner in which she'd finished against Williams, seemed to have the match on her racquet, striking 37 winners in all with her initially crisp ball-striking.
But it all started to unravel in the second set as the mistakes began to flow from the Australian, who ended up making 41 unforced errors. With each one, the volume from the legion of Filippino fans who follow their 'Alex' everywhere began to crank up.
"I really had to dig deep after Maya came out on fire, she came out ready," beamed Eala as she addressed the cheering crowd.
"She is coming off an amazing win against Serena. She played really well and handled herself really well in that situation, so congratulations to Maya."
Earlier, as Wimbledon's fourth day opened with the sun out and mercury rising, de Minaur needed just one hour 49 minutes to see off the often tricky 38-year-old left-hander Mannarino.
De Minaur won the first two sets in 38 minutes each, breaking twice in the first set and thrice in the second.
His own serve occasionally malfunctioned, being broken in each stanza, with the second delivery especially vulnerable.
But in the third, there was no such blemish, though he had to survive a lengthy service game at 2-2, which featured five deuces.
He followed up to break his downcast opponent twice to set up a third-round meeting with American Zachary Svajda, who defeated de Minaur's recent s'Hertgenbosch final conqueror Kamil Majchrzak in five sets.
The rising world No.66 Svajda won't be a pushover for 'Demon', having recently knocked out two Australians, Alexei Popyrin and Adam Walton, at the French Open.
"I'm very happy with a very clean performance today. I think going in, it was a very tricky match-up, and I did what I needed to do.
"There were some tough moments here and there, but I thought my serve got me out of trouble in certain key moments.
"I just love it here and I'm hoping I can stay here for a long time."
