Novak Djokovic has been here before, nipping at the heels of major title No. 21.

He had a chance at the U.S. Open last summer. Winning the men’s singles final against Daniil Medvedev would have been a signal moment in sports. Djokovic would have burst through the logjam he’d shared with Roger Federer and Rafael Nadal: 20 titles in majors, then the high-water mark in men’s tennis.

And Djokovic would have become the first male player since Rod Laver in 1969 to achieve a Grand Slam, capturing Wimbledon and the French, Australian and U.S. Open titles in the same year.

It wasn’t to be.

Then he seemed destined to record his 21st victory in a Grand Slam event at this year’s Australian Open, the major where he has emerged victorious nine times. He makes playing in the Melbourne hothouse look like a stroll through a shady summer garden.

But we know what happened instead.

Djokovic was detained and then deported after a tense standoff over whether he should be allowed to compete in Australia despite having proudly refused to be vaccinated against the coronavirus.

Point made and the moment lost by both the Australian government and one of the world’s best-known anti-vaccine athletes.

With the French Open underway, Djokovic is, at long last, trying again for his 21st major win. By virtue of his No. 1 ranking, he is the top seed in the men’s draw. “I’m going to Paris with confidence and good feelings about my chances there,” he said before the tournament.

He said much the same the last two times he reached for the grail of 21 Grand Slam events. But it was Nadal who notched that historic record first, ahead of Djokovic and Federer, when Nadal stepped back into the vaults of greatness and beat Medvedev at the Australian Open in jaw-dropping fashion.

Can Djokovic get out of the stall and tie Nadal? If he doesn’t do it soon he may begin drawing comparisons with an equally talented, complex and perplexing champion — Serena Williams, who remains stuck one major behind Margaret Court’s record mark of 24.

Like Williams, who at 40 is not playing on the tour and may be heading toward retirement, Djokovic faces snarling pressure to keep up with his peers. It is not getting any easier. On Sunday, he turned 35. His window is closing — the ability to call on match-to-match consistency narrows with each grinding season.

Consider all he has faced this year. Global anger over his determination to steer clear of vaccination. The hangover from the crushing loss in the final of the U.S. Open. The months when he looked like a meager facsimile of his old self on the tennis court.

After Australia, he was barred from playing in two big hardcourt tournaments, in Indian Wells and Miami, because the United States wisely required foreign visitors to be vaccinated to enter the country. Then came a stretch of choppy, angst-riddled play, which we had not seen from him in years. There were early-round defeats to the 123rd and 46th players in the world. Before adoring hometown fans, he struggled through the Serbia Open and crumbled in the finals. He fell in Madrid to the 19-year-old Spanish upstart Carlos Alcaraz.

Can Djokovic win his 21st at the French Open? There was little hint he would be up to the task until this month in Rome, at the last big tuneup before Roland Garros.

In Rome, it was all there again for Djokovic: lithe, deep and consistent returns, a pickpocket’s moxie during the tensest moments. Djokovic did not lose a set all tournament. In the final, where he defeated fourth-ranked Stefanos Tsitsipas, he took the opening stanza, 6-0.

He looked back on Australia and the brutal aftermath in a news conference and spoke of how the experience would not bow him. Djokovic promised to turn the jagged pain of having been barred from play and the pressure he felt from the backlash to his favor. “It will fuel me,” he said, steely eyed, “for the next challenge.”

Such a mind-set is as vintage Djokovic as his scythe-like down-the-line backhand.

Left unmentioned was how he has been hailed a hero among the anti-vaccine crowd for his refusenik stance, a view that is impossible to fathom when the coronavirus has caused the death of at least six million people across the globe. He has even vowed that if it came between choosing whether to be vaccinated or keep playing professional tennis, he would remain on the sideline.

His commitment to that stance is foolish, but his resistance offers a window into what makes Djokovic tick. Enduring stubbornness sets him apart more than his movement, consistency or dart-like accuracy.

He is a true believer — on the court and off it — and he has long latched himself to some of the self-help movement’s wildest false claims, everything from telepathy to the notion that loving thoughts can change the molecular structure of water.

Now you might think those ideas are pretty ridiculous. I sure do. But for Djokovic, clinging to belief in what may seem impossible has worked in astonishing ways.

We’ve seen it countless times on the biggest stages.

Remember his great escapes against Federer. The victories after facing two match points against Federer’s serve at the U.S. Open in 2010 and 2011. The marathon final win at Wimbledon in 2019, when he turned Federer away after the grass-court master held yet another pair of match points.

I was there and can still hear the frenzied Centre Court crowd yelling, “Federer! Federer! Federer!” ringing in my ears. But that’s not what Djokovic heard. He said after the match that as the roars rose like a storm for his opponent, he mentally converted the rhythmic chants to something that spurred him on — “Novak! Novak! Novak!”

Remember, too, the French Open of 2021, the bruising semifinal win against Nadal, the most recent act in the duo’s 58-match rivalry. The Serb followed that with a comeback from two sets down against Tsitsipas to win the championship.

Now the French Open is again underway. Victory at Roland Garros is as intense a journey as exists in sports — especially now, as players deploy a mix of power, touch, bounding topspin and athleticism in ways that not long ago would have been unimaginable.

Age and years of leg-churning wear on tour add another layer of difficulty. Look at Nadal, also 35 and currently battling foot and rib injuries severe enough to stir rumors of imminent retirement.

These two will again try to fend off a cast of younger stars in Paris. They will have eyes steady on one in particular: Alcaraz, who plays with the limitless élan of a teen and a veteran’s wisdom and strength.

All three are in the same half of the draw in Paris, bidding for a spot in the finals. Can Djokovic make it that far and finally win No. 21? I won’t bet against a player so capable of conjuring unshakable magic.