Stefanos Tsitsipas fought back from two sets down to defeat Rafael Nadal to reach the Australian Open semi-finals.
The Spanish second seed was stunned as Tsitsipas claimed a 3-6 2-6 7-6 (7-4) 6-4 7-5 victory in Melbourne.
Tsitsipas, 22, broke out into a huge smile, almost in disbelief, after converting his third match point.
Tsitsipas will face Russia's Daniil Medvedev in Friday's semi-final.
The 25-year-old won 7-5 6-3 6-2 as his childhood friend Rublev, who was seeded seventh, struggled in the 29C temperatures at Melbourne Park.
ATP Finals champion Medvedev now puts a 19-match unbeaten streak on the line against Tsitsipas, who needed over four hours to overcome Nadal.
"I'm speechless, I have no words to describe what just happened on court," said Tsitsipas, who was still out of breath in his on-court interview.
"My tennis speaks for itself. It is an unbelievable feeling to fight at such a level and give it my all on the court.
"I started very nervous, I won't lie. I don't know what happened after the third set. I flew like a little bird. Everything worked for me and the feelings are indescribable."