Fifteen-year-old American Coco Gauff beat Venus Williams at the Australian Open on Monday -the second time the teenager has dumped the veteran out in a Grand Slam first round.
Gauff surged into the second round in Melbourne with a 7-6, 6-3 victory over the 39-year-old and will play unseeded Romanian Sorana Cirstea next.
Gauff, ranked 67 in the world and a fast-rising star in tennis, similarly defeated the seven-time Grand Slam winner in the first round last year at Wimbledon.
"That was really difficult, she played really well," said the precocious teenager.
"I was really nervous for today's match.
"I was a bit shocked - I'm sure everyone was shocked - when they saw the draw come out but I'm glad I was able to get through it," Gauff added, referring to the repeat of their Wimbledon match.
Williams, formerly world No 1 but now ranked 55th, conceded the first-set tie break when she hit a routine backhand overhead into the net.
Gauff, remarkably unfazed by playing someone more than twice her age, held her nerve in the second set to claim Williams' scalp once more.
Victory over Williams at Wimbledon, and her run to the fourth round there - where she lost to eventual champion Simona Halep - propelled Gauff into the sporting limelight.
She went on to win her first WTA title in October in Linz, Austria.
Retiring former world No 1 Caroline Wozniacki urged the younger generation of players to "be nice to each other", saying locker-room friendships can last through life.
The Danish star, who is walking away from tennis after the Australian Open aged 29, lived to fight another day at Melbourne Park after crushing American Kristie Ahn 6-1, 6-3 in the first round.
"There's a lot of emotions, but I tried to keep them in check, and I thought I did that very well today," said Wozniacki, whose only Grand Slam triumph came in Melbourne in 2018.
"I think I'm just really trying to enjoy every moment."
Wozniacki announced her plan to retire in December to focus on other things, including starting a family with husband and former NBA star David Lee.
She said she will leave the game with lifelong friendships, not least best buddy Serena Williams, and encouraged the new women on the block to keep the locker room civil.
"I think in general my generation we had great friendships even from the juniors and we were a big group coming up and playing on the tour at the same time," she said.
"I think we have friendships that will carry on past the tennis.
"I don't know how it was before me. All I know is that Serena obviously played way before me and so did Venus, and they were both super nice to me and very open and have always been there for me.
"So I have had a great experience with them. Then I hope that the younger generation will also be nice to each other, because it's just a sport and we all try our best out here."
Naomi Osaka recently pointed to Wozniacki as a person who helped her when she was first burst on the scene and the Dane said it was important to give back to up-and-coming players.
"I don't even know what ranking Naomi was at this point, she came out of juniors, but I remember practising with her and thinking she has a great serve, she has some great shots," she said.