Rublev, 19, captivated a packed Louis Armstrong Stadium with his speed and stinging ground strokes to see off the 26-year-old Bulgarian, who not long ago was hailed as the next big thing in men's tennis and labelled 'Baby Fed.'
The Russian becomes the latest teenager to set the U.S. Open abuzz following 18-year-old Canadian Denis Shapovalov's upset of eighth-seeded Frenchman Jo-Wilfried Tsonga on Wednesday and 19-year-old American Frances Tiafoe's breathless opening round five-set loss to Federer.
The teenagers, none of whom are of legal age to celebrate their success with a drink in New York, have brought a jolt of youthful energy to the U.S. Open that looked set to be dominated by the veterans like Roger Federer and Rafael Nadal.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
(Reporting by Steve Keating in New York; Editing by Frank Pingue and Ken Ferris)
