ATP Finals 2019: Alexander Zverev denies illegal phone use despite damning vision

World No. 7 Alexander Zverev insists he was not using a phone, despite cameras appearing to catch the German in the act, during his ATP Tour Finals loss to Greece's Stefanos Tsitsipas on Thursday Morning.

Zverev was seemingly caught by cameras scrolling through a phone during the change of ends as the match began to turn in favour of his opponent.

The video appears to show a device light up, leading to an online media storm accusing the 22-year-old of brazenly breaking the ATP Tour's no-phone rules.

Players are prohibited from bribing their phones and other technological items onto court with them.

After the match, Zverev vehemently denied he had used a phone during play despite the damning vision.

He claimed he was unsure what reporters were referring to when questioned over the incident, instead offering that he may have simply just been fidgeting with a water bottle.

"It wasn't a phone," he said.

That wasn't enough to temper the Twitter-sphere who were unconvinced by Zverev's explanation.

Tsitsipas crushed defending champion Zverev 6-3 6-2 to book his place in the last four with a match to spare.

The 21-year-old, the first Greek player to qualify for the elite eight-man season-ender, backed up his opening win over Medvedev with a virtuoso performance.

The Greek broke in the eighth game when Zverev opted to serve and volley on a second serve but made a mess of a low volley and from that point on it was one-way traffic.

Zverev's level tailed off alarmingly in the second set and Tsitsipas wrapped things up with an ace.