Marcos Baghdatis was caught using his phone at a changeover during his US Open match against Gael Monfils.
He explained to the chief umpire that he was trying to send a text to his wife whilst he was losing to Frenchman Monfils.
At the changeover, after falling 4-1 behind in the second set, Baghdatis used his phone to contact his wife, attempting to disguise it in his towel.
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After the break was over, chief umpire Alison Hughes announced to the crowd at the Grandstand: "Code violation. Unsportsmanlike conduct. Warning, Baghdatis" after she had spotted what he was doing.
At the next changeover, Baghdatis attempted to defend himself to the umpire: "I cannot look at the time? (What) if I want to look at the time?"
Baghdatis was caught in the middle of his fourth round match against Monfils, as he was comfortably defeated 6-3 6-2 6-3 by the Frenchman.
The 2006 Australian Open finalist admitted why he had his phone during the tournament, and revealed that he was just sending a text to his other half.
"I was just writing a message to my wife."
Baghdatis did reveal that he thought the warning was fair: "Yeah, I mean, there is rules, so I guess I broke the rules. So I got a warning for it.
"No way I'm going to share what the message was. Nice try, though. No way."
The Cypriot added that it was not something he had ever tried on the tour before, but does not feel any regret for his decision.
The World number 44 now has to wait until the Australian Open to make a statement at a major tournament, as he did back in 2006 when he reached the final, but this crushing defeat by tenth seed Monfils will not help his confidence.
The Frenchman will now face his compatriot Lucas Pouille in the quarter finals, who defeated Rafael Nadal.