Alexander Zverev, 29, failed to recognise he had secured the US Open title after defeating home player Ben Shelton in the final. The German, who became a two-time Grand Slam champion, appeared to lose track of the score.
Following Shelton's long return on championship point, Zverev showed little reaction. He had already prepared to receive serve for what he believed was another game, having hit the balls to the other end of the court.
Zverev only realised his victory after looking at the scoreboard and the upper deck of the Arthur Ashe Stadium. He then smiled, marking an unusual celebration for a Grand Slam title win.
This US Open win follows Zverev's first Grand Slam title at the French Open in June and his appearance in the Wimbledon final in July. He is now the fourth man in the Open era to win his first two Grand Slam titles in the same year, with aiming for world No 1 now a realistic target.