Alexander Zverev says he definitely did not use his phone to cheat during his defeat to Stefanos Tsitsipas at the ATP Finals in London on Wednesday.
Footage captured by the Tennis Channel during the match appeared to show the 22-year-old scrolling through his phone, which was hidden away in his bag, during a change over in the second set of his 6-3, 6-2 loss.
The ATP forbid the use of unauthorized electronic devices on court to prevent match-fixing and on-court coaching.
"I don't know what they saw, but it was definitely not a phone," Zverev told reporters after the match when questioned about the incident, according to the BBC. "My phone was in the locker room. I always leave it there."
When asked what exactly it was that he was playing with in his bag, he said: "I mean, a water bottle? Empty water bottle maybe?"
The use of electronic devices on court, depending on the type of activity, could be considered a "corruption offence" according to ATP rules. This carries a maximum fine of $250,000, plus any on-court earnings, and a three year ban.
The ATP did not immediately reply to Business Insider's request for comment.
Zverev next takes on Danill Medvedev on Thursday, where a win will be enough to seal his place in the tournament's last four.