It wasn’t his opponent’s dazzling foot speed or the velocity of his serve that Andy Murray was still dwelling on a day after his match. The statistic that stuck with Murray, the 2012 U.S. Open champion, was how long his opponent, Stefanos Tsitsipas, took during his off-court breaks.

“Fact of the day. It takes Stefanos Tsitipas twice as long to go the bathroom as it takes Jeff Bazos to fly into space. Interesting,” Murray posted to Twitter on Tuesday morning, misspelling both the name of his opponent and the Amazon billionaire, but adding emojis of a toilet and a rocket ship for clarity.

On Monday, the third-seeded Tsitsipas had defeated Murray 2-6, 7-6(7), 3-6, 6-3, 6-4 in a match that turned early in the fifth set following an off-court break by Tsitsipas. Though two off-court breaks are allowed by the rules during best-of-five-sets matches, Murray was incensed when he saw Tsitsipas leaving the court after the fourth set, which Tsitsipas had won.

“Why are they allowed to do this?” Murray asked chair umpire Nico Helwerth with exasperation. “Why?”

Murray, 34, sat on his bench in Arthur Ashe Stadium, changed his shirt, draped an ice towel over his neck and hydrated, repeatedly glancing toward the court entrance. After a few minutes of sitting and bouncing his legs, Murray rose and wandered behind the baseline, bouncing a ball and hitting it gently against the video wall behind the court.

“What’s your opinion on this?” Murray asked Helwerth. “You’re umpiring the match. Give me an opinion: you think it’s good?” Murray then asked Grand Slam supervisor Gerry Armstrong, “You think this is OK, what’s happening?”

When Tsitsipas finally returned more than seven minutes after the last point had been played, he went to his bench, then walked to a cooler to get a bottle of water. He then sat down on his bench, and Murray shouted “Get up! What’s going on, get up!”

When the fans began to boo, Murray pumped his arms to encourage them.

Murray, still steamed, dropped his serve in the following game, and Tsitsipas held onto that break advantage the rest of the set. Murray said he had been prepared for Tsitsipas to take long breaks if the match wasn’t going his way, for which he believed Tsitsipas had a reputation.

“It’s just disappointing because I feel it influenced the outcome of the match,” Murray said. “I’m not saying I necessarily win that match, for sure, but it had influence on what was happening after those breaks. I rate him a lot. I think he’s a brilliant player. I think he’s great for the game. But I have zero time for that stuff at all, and I lost respect for him.”

Told of Murray’s comments, Tsitsipas, 23, said he hoped to speak to him directly.

“If there’s something that he has to tell me, we should speak, the two of us, to understand what went wrong,” Tsitsipas said. “I don’t think I broke any rules. I played by the guidelines, how everything is.

“I don’t know how my opponent feels when I’m out there playing the match; it’s not really my priority,” Tsitsipas added. “As far as I’m playing by the rules and sticking to what the ATP says is fair, then the rest is fine.”

Tsitsipas said his time off the court had simply been “the amount of time it takes for me to change my clothes and to walk back to the court.”

Acknowledging that players are often accused of abusing bathroom break or medical timeout rules to change the momentum of the match, Murray said he and other members of the player council had discussed rule changes that might make gamesmanship more difficult.

“If everyone else feels like that’s totally cool and there’s no issue with it, then maybe I’m the one being unreasonable,” Murray said. “But I think it’s nonsense. And he knows it, as well.”

In a statement, the United States Tennis Association said it “regards pace of play as an important issue in our sport,” citing its past implementation of visible serve clocks and warm-up clocks in recent years. “We need to continue to review and explore potential adjustments to the rules, whether for bathroom breaks/change of attire or other areas, that can positively impact the pace of play for our fans and ensure the fairness and integrity of the game,” the statement said.

Though tennis players are generally loath to weigh in on each other’s controversies, several couldn’t resist.

“Andy is right!” Milos Raonic, a Canadian who is missing the U.S. Open with a right leg injury, posted to Twitter on Monday night.

Asked after his first-round win on Tuesday if he felt Novak Djokovic was the favorite to win the U.S. Open, Alexander Zverev managed to fit in a dig at Tsitsipas in his answer.

“I think Stefanos can play well if he doesn’t go to the moon and back for a toilet break, that will also help,” Zverev said with a grin.

Zverev had previously leveled accusations of his own at Tsitsipas during their semifinal match at the Western & Southern Open in August, accusing him of using a mobile phone off court to illegally communicate about tactics with his coach and father, Apostolos.

Zverev reiterated his suspicions on Tuesday. “He’s gone for 10-plus minutes; his dad is texting on the phone,” Zverev said. “He comes out, and all of a sudden his tactic completely changed. It’s not just me but everybody saw it. The whole game plan changes. I’m like, either it’s a very magical place he goes to, or there is communication there.

“But I also don’t want to disrespect him,” Zverev added. “He is a great player.”

Tsitsipas denied cheating on Monday.

“I have never in my career done that; I don’t know what kind of imagination it takes to go to that point,” Tsitsipas said. “That’s not something I want to take seriously because it’s absolutely ridiculous to be thinking about that.”

Tsitsipas received support from the American player Reilly Opelka, who also took a lengthy break during his first-round win.

“We’re hydrating a lot; we have to use the bathroom,” Opelka said. “To change — my socks, shoes, my inserts in my shoes, shorts, shirt, everything, the whole nine yards, hat — it takes five, six minutes.

“If people don’t understand that, then clearly they’ve never spent a day in the life of a professional athlete or come close to it,” Opelka said.

Murray, who has spent most of his days in the life of a professional athlete, ended his news conference by saying that it was a shame that a five-hour match between two top players was eclipsed by stall tactics.

“I’m sitting in here after a match like that against one of the best players in the world, and rather than talking about how fantastic he is, how good he is for the game, how great it was for me that I was able to put on a performance like that after everything that’s gone on the last four years, I’m sitting in here talking about bathroom breaks and medical timeouts and delays in matches,” Murray said. “That’s rubbish. I don’t think that that’s right.”