Ben Solomon for The New York Times
Roger Federer suffered a stunning loss Tuesday night, falling in five sets to 78th-ranked Grigor Dimitrov in the United States Open quarterfinals, 3-6, 6-4, 3-6, 6-4, 6-2.
Dimitrov is the lowest-ranked player to beat Federer at the U.S. Open, surpassing 55th-ranked John Millman, whom Federer lost to in the fourth round last year.
But Dimitrov, 28, who won the Cincinnati Masters and World Tour Finals two years ago to reach a career-best ranking of No. 3, has long been thought of as one of the most talented players of his generation.