|2019 Nitto ATP Finals|
|Venue: O2 Arena, London Dates: 10-17 November|
|Coverage: Watch live coverage of one match per day on BBC TV, BBC iPlayer and online; Listen on BBC Radio 5 Live Sports Extra; Live text on selected matches on the BBC Sport website and app. Click here for Live Guide.|
Alexander Zverev has denied using his phone during his match against Stefanos Tsitsipas at the ATP Finals.
Zverev was asked about the incident at a news conference after he was seen touching something in his bag at a changeover during Wednesday's defeat.
The 22-year-old German, who lost 6-3 6-2 at London's O2 Arena, said: "I don't know what they saw, but it was definitely not a phone."
Rules state players cannot access any electronic devices during matches.
"My phone was in the locker room. I always leave it there," added Zverev.
Asked what he might have been touching, he said: "I mean, a water bottle? Empty water bottle maybe?"
An ATP spokesperson later said: "The ATP can confirm that there has been no breach of ATP rules concerning Alexander Zverev."