In addition to beating then-world No. 1 Rafael Nadal
at Wimbledon last July, the 20-year old defied expectations to down the Swiss master at the Madrid Open with a stunning 6-7 (7-2) 7-6 (7-5) 7-6 (14-12) victory.
The weight of meeting one of his childhood heroes on court did not appear to bow Kyrgios, who beat the elder statesman, and one of the most successful players in the history of the sport, in just over two and a half hours.
"Before the match I didn't feel nervous or anything like that," said Kyrgios, who on Sunday missed out on his first top-level title when he was beaten in the Estoril Open final in Portugal.
"I was just excited to get out to the court. I've been playing well recently on the clay, so I knew I had a good chance to go out there and do well. I stuck to my game and served well and I got the win."
After the younger player -- ranked 35th in the world -- broke his serve in the first game, Federer used his greater maturity to steady the ship, and ended up taking the set to a tie break.
There was some bad temper from both players during the first set, with Kyrgios cautioned for unsportsmanlike behavior.
Federer gamely tried to see off the Australian, but ultimately youthful zest won out over experience. After the match, Federer was reflective.
"It's a big stage, you know? And he -- he has nothing to lose, he has no fear and he's got a great game so he could rely on his serve so much that it keeps him in the match regardless of how he plays from the baseline," the 17-time grand slam winner said.
His serve indeed was on fire, with Federer only able to win 18 of 85 first-serve return points.
"All he needs to do is string a few good shots, a few good points together when it really matters. It was one of those matches but no doubt about it, it was impressive," said Federer, who on Sunday won the 85th title of his glittering career at the inaugural Istanbul Open in Turkey.
Krygios, the youngest player in the ATP Tour's Top 50, took to Twitter after the match to admit that the encounter had left him "buzzing."
He next faces John Isner of the U.S. in the third round, while third seed Nadal -- who beat 54th-ranked American Steve Johnson in his opening match -- will continue the defense of his title against Italy's Simone Bolelli.
World No. 4 Nadal, who is struggling on his favorite clay surface ahead of the French Open, will again face Kyrgios if they both reach the semifinals.
"I know things are going to work out," said the Spaniard, who lost in the last 16 in Barcelona and was beaten in the Monte Carlo semis by top-ranked Novak Djokovic.
"I haven't lost my game. I just need to build my confidence and it'll work out. I know that either sooner or later it will come back. That's what I want to think. I'm convinced about it. It's matter of time. Let's see when it happens."