(CNN)Stefanos Tsitsipas was booed by the crowd during his second-round US Open win over Adrian Mannarino after taking another extended toilet break.
The world No. 3 angered Andy Murray, his opening-round opponent, during their five-set epic on Monday with two long trips to the bathroom, leading the Scot to call out Tsitsipas after the match.
During his 6-3 6-4 6-7 6-0 win over Frenchman Mannarino on Wednesday, Tsitsipas was again off-court for more than eight minutes and was jeered by sections of the crowd on his return.
Such was the length of the delay, Mannarino asked to hit some balls during the wait to ensure he didn't stiffen up, something Murray said he struggled with due to Tsitsipas' breaks.
Tsitsipas insisted the breaks are "important" to him.
"First of all, you carry less weight on you with all the sweat," he told reporters. "You feel rejuvenated, you feel fresh, and you don't have all the sweat bothering you and coming in your face, on your fingers, everywhere all over your body. It makes you feel better.
"For me, it is important to take that break. For someone else probably not and everyone has his own time. I try and be as quick as I can. Sometimes I just need a bit more time. That's all."
When told by a reporter that he was off-court for more than seven minutes, Tsitsipas replied: "I would like to know, what's the rule ... the rules are there to be followed, no?
"If I break a rule, sure, I'm guilty. I agree, I'm not doing something right. If I'm staying within the guidelines, then what's the issue?"
Tsitsipas tried to respond to Murray's criticism by asking a reporter how long the Scot had taken for a toilet break during his 2012 US Open final win over Novak Djokovic in 2012, but didn't get the answer he was hoping for.
When told by a reporter that it was less than three minutes, Tsitsipas asked: "Okay, so three minutes more makes a difference?
"I haven't done anything wrong," he added. "So I don't understand. The people love the sport, they come to watch tennis. I have nothing against them. I love the fans.
"But some people don't understand. That's all. They don't understand. They haven't played tennis at (a) high level to understand how much effort and how much difficult(y) it is to do what we are doing.
"Sometimes we need a short break to do what we have to do."
Tsitsipas will now face Spanish teenager Carlos Alcaraz in the third round.