Andy Murray criticises Novak Djokovic: 'We need to respect the rules'

World number one Djokovic confirmed he had contracted Covid-19 on Tuesday, becoming the fourth player infected during the Balkan series, which featured big crowds and players partying without social distancing.

Grigor Dimitrov, Borna Coric and Viktor Troicki also returned positive tests, with Djokovic criticised from all quarters for allowing his Balkans tournament to descend into a viral nightmare, with scenes broadcast on social media of players enjoying themselves in a Belgrade nightclub.

Now Murray has become the latest voice to cast doubt over the merits of the tournament.

"Obviously it's not surprising how many players have tested positive when you see the scenes and the images and the videos from the tournament and the players party with no social distancing in place," Murray said. "I've seen some people say this puts the US Open in doubt but the measures and the protocols they have in place are completely different to what was going on in Serbia and Croatia.

Murray enjoyed a winning return to action after a seven-month injury lay off as he beat Liam Broady in the 'Battle of the Brits' charity tournament at the national tennis centre in west London.

The twice Wimbledon champion and former world number one eased to a 6-2 6-2 victory over the British number six in his first competitive match since the Davis Cup Finals in November.

The week-long event, organised by Murray's brother Jamie while professional tennis remains suspended due to the Covid-19 pandemic, is being played behind closed doors with strict health protocols in place.

"It was OK, I served well throughout the match," Murray added. "Didn't hit the ball that well from the back of the court, wasn't timing the ball well. For a first match in seven months and not been practising much, so it was alright. Last time I picked up my own balls was when I was about 17. Although we do it all the time in practice."