BELGRADE (AFP, REUTERS) - Covid-19 has been nothing but a public relations disaster for Novak Djokovic.

The world No. 1 was criticised for breaking lockdown rules to train in Spain and raised eyebrows by insisting he would not be prepared to vaccinate against the coronavirus.

The Serb also described planned limits on players' entourages at the US Open as well as strict measures to keep players apart to protect them from the virus as "extreme" and "impossible", again putting him at odds with much of public opinion.

Then came this week's Adria Tour fiasco, where Djokovic, Grigor Dimitrov, Borna Coric and Viktor Troicki all tested positive after taking part in the event organised by him. Social distancing was minimal at the event and matches were played in front of thousands of fans.

His latest misstep has caused some to question his presidency of the ATP Player Council, which advises the ATP board.

"I think there's a lot of his peer group who are scratching their heads," veteran coach Paul Annacone told Tennis.com.

Martina Navratilova, who won 18 Grand Slam singles titles, tweeted: "Yikes... this is not good and it's a pattern... What now, US Open? Roland Garros? We have a lot of work to do."

Brazil's Bruno Soares, a doubles player who sits on the Player Council, called the Adria Tour a "horror show".

ATP chairman Andrea Gaudenzi said it was a lesson for other tournaments.

"It's a little bit like when you tell your kids when they try to learn to ride the bike to wear the helmet," Gaudenzi said. "It's 'no, no, no'.

"And they ride the bike, they fall, and then they wear the helmet."

On Thursday, outgoing Wimbledon chief Richard Lewis added to the chorus of criticism, calling the images of the players hugging at the net, playing basketball together and partying "disappointing" and saying tennis must learn its lesson.

Lewis, who will step down as the chief executive officer of the All England Lawn Tennis Club next month, told British media he hoped everyone made a speedy recovery but that the mistakes of the event must not be repeated.

"The images were disappointing and I think that ... what needs to come out of it is everybody involved - not just players, but administrators, organisers, entourages - understands that the protocols, rules and regulations are in place for a reason.

"That's a really important lesson to learn."

With the Djokovic heading the men's players' council, Lewis urged athletes to play a bigger leadership role.

"I would hope from an organisers' point of view - let's say the US Open and Roland Garros, but also the other international tournaments - that protocols will be easier to enforce and observed than they otherwise might have been," said Lewis.

"I sincerely hope that when international tennis tournaments resume, the sport will be more disciplined and follow the protocols in place at whatever tournament is being staged at the time."

Prior to the Covid crisis, Djokovic had already raised eyebrows for unusual claims including that human emotions can change the quality of water.