On Sunday, Novak Djokovic lost his legal challenge to remain in Australia, clearing the way for the country to deport him and denting his hopes of competing in the Australian Open.

For even exceptionally conditioned tennis champions, the window for winning Grand Slam titles narrows with age. No amount of experience or self-belief can compensate for the inevitable physical decline in explosiveness, nor can it forestall the rise of younger challengers with bigger games and comparable conviction.

This is the calculus now facing Novak Djokovic, 34, after Australia’s immigration minister, Alex Hawke, revoked his visa Friday, citing “health and good order” grounds amid a falsehood on Djokovic’s immigration form regarding international travel he had taken in the 14 days before his Jan. 5 arrival at Melbourne’s Tullamarine Airport to compete in the upcoming Australian Open.

Djokovic’s lawyers are appealing the decision, and a judge agreed at a hearing late Friday not to seek his removal from the country until the court proceedings are resolved. If Djokovic’s bid fails, he would be deported.

Hawke’s decision casts new doubt on whether Djokovic, a nine-time Australian Open champion, will be allowed to compete for a men’s record 21st major singles title when the season’s first Grand Slam event gets underway Monday at Melbourne Park.

Djokovic, who is not vaccinated against the coronavirus, blamed his agent this week for what he called “human error” on his travel declaration, which falsely said he had not traveled internationally in the two weeks before he arrived in Australia. He also apologized for interacting with journalists for a French sports publication Dec. 18 despite learning two days earlier he had tested positive for the virus.

Hawke’s decision — announced the day after tournament officials unveiled the draw with Djokovic seeded first — is the next chapter in a 10-day circus over Djokovic’s eligibility. It has roiled Australian citizens, outraged Djokovic’s Serbian compatriots, pitted Australian Prime Minister Scott Morrison against state officials in Victoria and called into question the impartiality of Tennis Australia, the governing body that runs the nation’s Grand Slam event.

If Djokovic is deported, the opportunity to make men’s tennis history at this year’s Australian Open falls solely to Rafael Nadal, 35, who is tied with Djokovic and 40-year-old Roger Federer (who is not competing as he recovers from knee surgery) with 20 majors.

Hawke’s decision represents a blow to Djokovic, the world’s No. 1 men’s player, on two levels.

It moves him one step closer to being denied one of four Grand Slam title opportunities this season. And although he remains a national hero in his native Serbia, in the eyes of much of the tennis world, the episode has tarnished his integrity and a legacy he is still constructing.

Djokovic would have entered this year’s Australian Open without a hitch, of course, had he gotten vaccinated against the coronavirus, which was required of all players unless they documented an approved medical reason that made them exempt.

Problems arose immediately upon Djokovic’s arrival at Melbourne’s airport when Australian Border Force officers ruled invalid the medical exemption from vaccine requirements that the player had been granted by Tennis Australia and state health officials in Victoria.

Djokovic’s reason for requesting the exemption was that he had a recent case of the coronavirus, diagnosed in mid-December. That fell short of the national standard for valid contraindications — conditions such an allergy to a component of the vaccine that would imperil a person’s health.

After Djokovic spent five days in a government-designated hotel for immigrants in similar limbo, a federal judge overturned the government’s decision to deny his visa on procedural grounds.

Before the controversy over his medical exemption, Djokovic seemed all but assured of surpassing Nadal and Federer for the men’s record tally of majors. His best chance, in fact, was the first Grand Slam of the 2022 season.

No man or woman has won more Australian Open titles in the sport’s Open Era than Djokovic. The lightning-fast hard court of Rod Laver Arena is tailor-made for his potent blend of offense and defense.

“If you have asked me six months ago or nine months ago, even at the U.S. Open [in September], I thought he was well on his way to smashing the men’s record,” Brad Gilbert, a former touring pro and coach-turned-ESPN analyst, said during a conference call Wednesday. “I thought he might [win] 25 to 27 majors.”

That is less certain now, as the next generation’s challengers round into form and believe that Grand Slams are no longer the fiefdom of Djokovic, Nadal and Federer. Among them: Russia’s Daniil Medvedev, who routed Djokovic in straight sets to win the 2021 U.S. Open and deny the Serb’s bid for the rare calendar-year Grand Slam; Germany’s Alexander Zverev, the world’s No. 3 player and a 2020 U.S. Open finalist; and fourth-ranked Stefanos Tsitsipas of Greece, who was edged by Djokovic in a five-set 2021 French Open final.

Moreover, if Djokovic continues to refuse the vaccine, it’s possible he will face additional hurdles entering France, England and the United States, which host the season’s remaining Grand Slams.

French officials have indicated that he will be able to compete at Roland Garros, where he is the defending champion but Nadal holds a record 13 titles.

England requires unvaccinated visitors to present a negative coronavirus test taken two days before traveling, quarantine for 10 days upon arrival and follow up with subsequent negative tests.

The United States, at present, requires non-U.S. citizens to be fully vaccinated to travel to the country, with limited exceptions.

The pandemic’s future course — whether the omicron variant fizzles, whether new variants emerge — will largely dictate the freedom of unvaccinated athletes and others to travel from one country and continent to another.

For tennis pros, the freedom to travel is essential to competing. The sport’s four Grand Slam events are held on three continents. The nine Masters 1000 events in men’s tennis, the most prestigious tier next to the majors, are held in six countries: Canada, China, France, Italy, Spain and the United States.

Will these countries require visitors show proof of full vaccination? Will they offer exemptions for the non-vaccinated? If so, how liberal will the exemptions be?

“There will be numerous tournaments and other majors [in which] he will no longer be able to participate if he chooses to stay unvaccinated,” Gilbert said of Djokovic. “How are you going to sustain on tour? … It’s going to be a very difficult proposition to be a full-time player being unvaccinated.”

Regardless of Djokovic’s pending legal appeal, there is no doubt he will retire as one of the game’s greatest players — if not the greatest.

Still, his international profile — and his reputation among some of his fellow competitors — has been tainted by the episode, which included maskless interactions with a group of children after he tested positive, although Djokovic claimed he had not yet received the test result.

His blitheness amid the pandemic’s highly contagious omicron variant runs counter to assurances he gave in the summer of 2020, after he, his wife, fellow pro Grigor Dmitrov and a handful of coaches contracted the coronavirus during an exhibition he staged in Serbia and Croatia without safety protocols to guard against transmission. Djokovic apologized afterward and vowed to be more vigilant going forward.

Djokovic’s visa controversy has galvanized his support in Serbia, where his father, Srdjan, has characterized him as a Christ-like martyr and victim of political persecution. But empathy among fellow tennis players, who have largely steered clear of the controversy, is waning.

Tsitsipas, 23, who chose to get vaccinated to compete in Australia despite his own skepticism, told New Delhi-based WIO News this week that Djokovic was “playing by his own rules” and making other players “look like fools” for flouting the requirement.

More than 90 percent of the top 100 men have been vaccinated, according to the Association of Tennis Professionals.

If the careers of Federer, Nadal, and Djokovic ended today — amid the three-way tie with 20 majors — Djokovic’s achievements still make a compelling case that he is the best to ever play the game. He boasts a superior head-to-head record against both (27-23 over Federer; 30-28 over Nadal).

He also holds the men’s record for weeks ranked No. 1 (356, as of Monday). Only Steffi Graf, with 377, has more.

In the view of many sports fans, statistics are the sole metric of greatness. Others take a broader view.

Said the late Arthur Ashe, a three-time Grand Slam champion, former U.S. Davis Cup captain and humanitarian: “True heroism is remarkably sober, very undramatic. It is not the urge to surpass all others at whatever cost but the urge to serve others at whatever cost.”