The high temperatures and humidity in New York this week led tournament organisers to introduce a new rule permitting a 10-minute break between the third and fourth sets during men’s matches.

Players are not allowed to talk to their coaches, which is exactly what Murray said he saw Verdasco doing after finishing a cold shower.

The Scot was furious that it was he who alerted officials to the incident, telling umpire Nico Helwerth when he returned to the court: “I had to tell them because no-one knows the f***ing rules.”

Discussing the matter after Verdasco’s 7-5 2-6 6-4 6-4 victory, Murray said: “I went and told the supervisor. I said, ‘What are you guys doing? I mean, there’s clear rules here and you’re allowing this to take place. I don’t get it.’

“Then he ran through, ‘Oh, you’re not allowed to speak.’ They obviously weren’t in there for long, but you’ve got to do better than that. This is one of the biggest events in the world.”

Verdasco flatly denied any such rule breach had taken place, claiming that while his coach was in the locker room, he spoke only to another player, Marcos Baghdatis, and the Cypriot’s coach.

Verdasco said: “Obviously if Andy says that, I don’t want to say that he lies, but I didn’t talk one word with my coach or any one member of my team. I know exactly the rule and I don’t want to be the one breaking it.”

With tournament organisers apparently unable to shed any light on what happened, it was a case of one man’s word against the other – and Murray was determined to make sure it was he who had the last one.

In a post on Instagram, Murray wrote: “I’m off to get a health check as apparently I’ve started imagining things,” followed by the hashtag #liarliarpantsonfire.

Nick Kyrgios, who has history with Verdasco, also weighed in on the debate, saying of the coaching accusations on Twitter: “Let’s be real, very believable because it is Verdasco lol.”