John McEnroe: Novak Djokovic missing U.S. Open over COVID-19 vaccination 'a joke'

All-time tennis great Novak Djokovic famously missed out on playing in this year's Australian Open due to his well-noted objections over receiving one of the safe and available COVID-19 vaccines but went on to win the summer's Wimbledon final. 

As things stand today, Djokovic is unable to participate in the upcoming U.S. Open due to the country's mandate that requires travelers to show proof they're fully vaccinated against COVID-19 to board flights and enter the nation. The 35-year-old previously vowed he'd miss Grand Slam tournaments over vaccine requirements, and a fellow tennis icon seemed to recently have his back regarding such rules. 

Per Reuters (h/t ESPN), current ESPN analyst and tennis legend John McEnroe, a four-time U.S. Open champion, believes Djokovic should be able to take the court when the Grand Slam's main draw gets underway this coming Monday. 

"I don't think it's fair," McEnroe remarked. "I think it's a joke. I would have had the vaccine and gone and played, but he's got very strong beliefs and you have to respect that. At this point, in the pandemic, we're two-and-a-half years in, I think people in all parts of the world know more about it, and the idea that he can't travel here to play, to me is a joke."

Djokovic is chasing history, as he is on 21 career Grand Slam singles titles. Rafael Nadal holds the men's all-time record with 22 Slams, while Roger Federer has 20. 

Depending on all that occurs over the next several years, Djokovic may eventually feel regret over his choices if he doesn't surpass or catch Nadal in the Grand Slam singles titles category.