Novak Djokovic was on course to break the men's record for Grand Slam titles but his aversion to receiving the COVID-19 vaccine could jeopardise his participation in future tournaments, ESPN tennis analyst Brad Gilbert says.
It remains unclear whether Djokovic, the winner of a record-equalling 20 Grand Slam titles, will be allowed to compete at next week's Australian Open amid a dispute with the Australian government over his medical exemption to taking the vaccine.
A judge released the world No.1 from an immigration detention centre this week after his visa was cancelled by border officials.
Djokovic has since blamed human error for a mistake in his immigration paperwork and apologised for breaking isolation for a photoshoot when he had COVID-19 last month, raising the prospect that he could still be deported.
"If you'd have asked me six months ago or nine months ago, even at the US Open, I thought he was well on his way to smashing the men's record," Gilbert, a coach and former player, says.
"I actually thought that he would end up passing Margaret Court. I thought he might get 25 to 27 majors."
Australian Court, who retired in 1977, holds the all-time record of 24 Grand Slam singles titles.
"But I think there will be numerous tournaments and other majors he will no longer be able to participate in if he chooses to stay unvaccinated."
Djokovic could struggle to get into the United States for March's Indian Wells and Miami Open Masters 1000 tournaments, as well as events in Canada and other countries.
"I'm not sure every country has medical exemptions for COVID. There might be some for an irregular heartbeat, but it's going to be a very difficult proposition to be a full-time player being unvaccinated," Gilbert added.
ESPN analyst and former player Pam Shriver said that if Djokovic is deported, it would be a "big blow" to his already controversial legacy, which includes his default from the 2020 US Open after he inadvertently hit a line judge in the throat with a ball he struck in anger.
"He's already kind of had enough moments and enough question marks to definitely tarnish his legacy, but certainly nothing will ever tarnish his record 20 majors and counting, his weeks at No.1, his winning of all of the Masters Series twice," Shriver said.