Novak Djokovic hopes of claiming an unprecedented 21st Grand Slam title could be dashed permanently unless the Serb changes his stance, with rules on travellers who are unvaccinated against Covid-19 tightening.
With the pandemic now entering a third year some tournaments, including the French Open, are reconsidering exemptions.
The Serbian, who has not been vaccinated, was deported from Australia on Sunday ahead of the Australian Open after losing a court case to have the cancellation of his visa overturned.
Djokovic is automatically disqualified from obtaining a visa for Australia for the next three years, denying him the chance to add to his record nine titles at Melbourne Park. But Prime Minister Scott Morrison has left the door open for a possible return next year should the Serb comply with Covid entry requirements.
The world No 1, however, faces more immediate hurdles in his bid to overtake Swiss Roger Federer and Spaniard Rafa Nadal, with whom he is tied on 20 major titles, as he could be barred from the French Open as things stand.
The French Sports Ministry said on Monday there would be no exemption from a new vaccine pass law approved on Sunday, which requires people to have vaccination certificates to enter public places such as restaurants, cafes and cinemas.
"This will apply to everyone who is a spectator or a professional sportsperson. And this until further notice," the ministry said.
"As far as Roland Garros is concerned, it's in May. The situation may change between now and then and we hope it'll be more favourable. So we'll see but clearly there's no exemption."
The 34-year-old's immediate schedule is not yet clear, but one event likely circled on the Serb's calendar is the Dubai Duty Free Tennis Championships starting February 21.
A frequent visitor to Dubai, Djokovic was rewarded with a UAE golden visa shortly after winning the 2020 tournament. It was his fifth Dubai title.
A spokesperson for the event confirmed all players would need to provide negative PCR tests before being allowed into the UAE, adding players will then need to "adhere to the testing protocols and processes stipulated by the ATP and the WTA".
Organisers of the Monte Carlo Masters, which Djokovic has won twice, are awaiting French government guidelines for the next edition in April, while Wimbledon organisers AELTC are also yet to finalise safety arrangements for the major.
However, England's Lawn Tennis Association said entry requirements for its events, some of which serve as Wimbledon warm-ups, would be determined by the government.
Currently, unvaccinated people can enter England but must isolate for 10 days.
A US Open representative said last week that the year's final major would follow New York City Department of Health guidelines.
Djokovic could have trouble even getting into the United States, because foreign air travellers have had to be fully vaccinated since November and provide proof before boarding flights, with limited exceptions.
The US Centers for Disease Control and Prevention has said there are no exceptions for vaccine requirements "for religious reasons or other moral convictions".
The Serb, who is among three ATP players in the top 100 yet to be vaccinated, could also face issues ahead of the Italian Open in Rome in May due to tough anti-Covid restrictions in Italy.
Madrid Mayor Jose Luis Martinez-Almeida told La Sexta TV station on Monday that it would "be great" to have Djokovic play in the April 26-May 8 Madrid Open, which he has won three times, though the government would be the arbiter.
Spain requires visitors to prove they have been vaccinated, had a recent negative test, or have immunity based on recovery.
Answering a question on whether Djokovic would be allowed to enter Spain to compete after Australia deported him for being unvaccinated against Covid-19, Prime Minister Pedro Sanchez said: "Any sportsperson who wishes to compete in our country must comply with the health rules of Spain".
The fallout from Djokovic's deportation could cost the Serb in sponsorship, too.
French apparel brand Lacoste, a sponsor of Djokovic, said it would contact the world No 1 "as soon as possible" to review events in Australia.