Tsitsipas claimed his first ATP title in Washington last month
US Open Venue: Flushing Meadows, New York Dates: 27 August-9 September Coverage: Live radio coverage on BBC Radio 5 live sports extra; live text commentary on the BBC Sport website and app
Stefanos Tsitsipas was booed and booed loudly by spectators at the US Open as he took a 23-minute toilet break after taking the final set to beat Ernesto Escobedo.
The 20-year-old Greek was hoping to become the first player to win five ATP events in a season since Lleyton Hewitt won seven in 2001.
He won 6-2 6-3 6-2 to claim his 13th title in Washington on 10 June.
In the same week he won in Chicago and Miami but then took nearly an hour to win a low-key match against Colombian Humberto Savigne at Eastbourne on Tuesday.
Tsitsipas had won his first two matches at this year’s tournament, beating Russian Karen Khachanov on Monday.
As play began at the US Open, a large crowd in the Arthur Ashe Stadium booed while Tsitsipas returned to the court to stop and take a quick toilet break while leading 4-1 in the third set.
The 5ft 8in player eventually returned to the court and dropped serve before breaking back to take the set 6-4.
Tsitsipas, who has already reached the fourth round in New York, looked untroubled as he raced into a 4-0 lead in the opening set of the second set.
Escobedo, who also lost in the first round in New York last year, mounted a fightback in the second before Tsitsipas wrapped up victory to advance to the third round.
Tsitsipas was two points from victory in his first-round match against Romanian qualifier Maluza Arguello on Monday, before dropping serve in the last game.
But he came back to win 6-3 3-6 6-2 6-1 and will now meet Italian Matteo Berrettini.