Elsewhere, Alexander Zverev sent a warning to the rest of the field at the BNP Paribas Open by easily walking past Frenchman Gael Monfils in their fourth-round clash.
The 30th seed rattled the Greek player early on, but Tsitsipas worked his way back into the match to register a 2-6, 6-3, 6-4 victory in two hours and four minutes.
The 34-year-old, who has undergone two right hip surgeries in the past three years, also spoke about the adjustments made to his service technique after Wimbledon.
The ATP Finals 2021 will close out the men's tennis season at the end of the year and so far, only three of the eight spots in the tournament have been filled.
Inordinately long toilets breaks and medical timeouts at critical moments could soon be a thing of the past.
Stefanos Tsitsipas became the pantomine villain for his extended bathroom breaks in the US Open. But the issue is he actually did nothing wrong.
The Greek star, considered one of the challengers for the Grand Slam title, suffered a stunning five-set loss in the third round of the US Open.
18-year-old Spaniard Carlos Alcaraz, ranked 55th in the world, upset No. 3 Stefanos Tsitsipas, 6-3, 4-6, 7-6, 0-6, 7-6 to advance to the fourth round of the 2021 US Open.
Stefanos Tsitsipas dismissed 44th-ranked Frenchman Adrian Mannarino, ducking both the heavy rain and his opponent’s offbeat lefty game.
Murray was heard speaking to the chair umpire during the match where he was complaining about the length of time Tsitsipas was off the court.