American teenager stuns former World No. 1 at 2025 Australian Open

The five-set marathon, which lasted four hours and 49 minutes, was ultimately decided in a fifth-set tiebreaker that Tien clinched 10-7. The American showed incredible resiliency, winning two break points to draw level. At that point, an irate Medvedev became demonstrative and ultimately committed two unforced errors to lose the match. In many ways, the Russian was forced into submission.    

After the biggest win of his career, Tien thanked the late-night crowd that stuck around until the wee hours of the morning. 

Tien walked into the Melbourne major with confidence after breezing through the qualifiers and reaching the finals at December's Net Gen ATP Finals. He will next face unseeded Frenchman Corentin Moutet in the third round, with a realistic chance of going deeper in the draw. 

Tien's win on Thursday meant that the 2025 Australian Open has replicated a feat not seen at a major since the 2006 French Open.