Czech teenager Jakub Mensik upset three-time Grand Slam finalist Casper Ruud at the Australian Open before warning the tournament's top seed: "New The blood is coming."
The Norwegian sixth seed had no reaction to the 19-year-old's power and intensity as he became the highest-ranked men's seed on Wednesday.
Mencic recorded the biggest victory of his fast-growing career with a 6-2, 3-6, 6-1, 6-4 sweep, while Rudd became another team challenging the established order. A casualty of the tennis budding youth team.
On Tuesday, 18-year-old NextGen champion Joao Fonseca defeated ninth seed Andrey Rublev.
It was the first time two teenagers had beaten a top-10 player at a Grand Slam since Novak Djokovic and Andy Murray achieved the feat at Wimbledon in 2006.
The third teenager, 19-year-old American Learner Tien, will face fifth seed Daniil Medvedev on Thursday.
"It's great to always have new blood coming in. We can see that tennis is moving forward," said Mencic, ranked 48th.
"We can see different or new names in the tournament. It's really great for the fans, for tennis, for everything. New blood is coming!"
However, world number two Alexander Zverev had no problems as he defeated Spaniard Pedro Martinez in straight sets to advance to the third round.
The German proved too hot for his 27-year-old compatriot, beating him 6-1, 6-4, 6-6 in less than two hours at Rod Laver Arena He was defeated by a score of 1.
Previously, ten-time champion Novak Djokovic surpassed Roger Federer to become the player with the most Grand Slam singles matches entering the third round.
The 37-year-old won 6-1, 6-7 (4/7), 6-3, 6-2 on Rod Laver Arena against a fearless Czech 26th seed Stout resistance from Portuguese qualifier Jaime Faria. Thomas Machak.
This is the 430th time Djokovic has won the most singles matches in the Open era, either male or female, at a Grand Slam, ahead of Federer (429) and Serena Williams (423). .
No one has played 400 or more.
"I love this sport, I love competing," said Djokovic, who reached the third round in Melbourne for the 17th consecutive year.
"I try to do my best every time. I have been competing in Grand Slam tournaments at the highest level for more than 20 years.
"Winning or losing, I put my heart and soul into the court. I'm lucky to be able to make another record.
"Grand Slam matches and Grand Slam wins are the most important in our sport. Of course I'm very excited about it," he added.
In the final match of the women's draw, world No. 3 Gauff fought back from 5-3 down in the second set to beat Britain's Judy Burlage 6-3, 7-5.