The crowd serenaded the No. 3 seed from Greece with a rendition of “Happy Birthday” as he was presented with a white sheet cake decked out with fresh fruit.
“One of the best feelings you can experience on a tennis court,” said Tsitsipas, who is ranked No. 3 and lost the French Open final to Novak Djokovic in five sets.
Tsitsipas dominated his Russian opponent, saving both his break points and winning 74% of his service points.
He will face sixth-seeded Casper Ruud of Norway in the quarterfinals Friday. They met at the Madrid Open in May, with Ruud winning in straight sets in the round of 16.
“I’m looking for a change, looking for a switch-up this time,” Tsitsipas said.
Ruud beat Dusan Lajovic of Serbia 6-4, 6-3.
American Reilly Opelka also advanced, beating Lloyd Harris of South Africa 4-6, 7-6 (6), 7-6 (4). Opelka will face 10th-seeded Roberto Bautista of Spain, a 6-3, 3-6, 7-5 winner over eighth-seeded Diego Schwartzman of Argentina.