Novak Djokovic at centre of 'disgusting' scenes against Rafa Nadal

Tennis legend John McEnroe has blasted the 'disrespectful' French Open crowd after they once again booed Novak Djokovic before his quarter-final clash with Rafa Nadal.

Djokovic and Nadal did battle at Roland Garros on Tuesday for the 59th time in their storied careers, with Nadal prevailing 6-2 4-6 6-2 7-6 (4) to advance to the semi-finals.

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But there were ugly scenes as both players walked out onto court, with spectators on Court Philippe-Chatrier loudly booing Djokovic.

The World No.1 has never experience much crowd support at Roland Garros and was never going to have the crowd on his side against the 13-time champion Nadal.

Nevertheless, American legend McEnroe was still shocked to hear the boos that rained down on Djokovic on Tuesday.

“No other player has had to deal with more adversity," McEnroe said on Eurosport.

"It is unfair, I’ve got to say that. This guy has turned lemons into lemonade more often than any player in the history of tennis, and if you don’t think it bothers him, you’re nuts.

"He is so mentally tough that he can deal with this and somehow channel that anger and frustration over what he feels is a lack of respect - and I feel it is too.”

Spectators also took aim at Djokovic in an ugly moment in the fourth set when the World No.1 angrily smashed his racquet into the net after an unforced error.

Speaking on Monday, McEnroe said the booing wouldn't affect Djokovic because he's so used to it at this stage in his career.

“He does it better than anyone I’ve ever seen,” McEnroe said of the way Djokovic feeds off the negative energy and uses it to his advantage.

“I didn’t do it as well. I felt like it affected me more than it helped me.

"I think there were times where it fuelled me, but he has done it consistently. He’s a remarkable player and person.”

TV viewers also took to social media to condemn the crowd's treatment of Djokovic, labelling it "disgusting" and a "disgrace".

Alexander Zverev gets past Carlos Alcaraz

Alexander Zverev earlier advanced to the semi-finals after an upset win over highly-fancied Spanish youngster Carlos Alcaraz.

The German World No.3 won 6-4 6-4 4-6 7-6 (9-7) in three hours and 18 minutes of breathtaking tennis on Tuesday.

It was Zverev's first win over a fellow top-10 player at a grand slam in a dozen attempts, overcoming the Spanish teenager in a pulsating quarter-final.

Billed as the entree before the Nadal-Djokovic showdown, the match proved a feast in itself.

Zverev raced to a two-set lead with Alcaraz making a string of unforced errors. But then the sun dipped behind the stands and the 19-year-old woke up, taking the third set and holding set point in a gripping fourth-set tiebreak.

But Zverev saved it before winning on his second match point.

"I knew I had to play my best all match," said Zverev. "I am extremely happy I won the tiebreak.

"The match was turning his way. I told him at the net he will win this tournament. I hope I can win it before he starts beating us all."

The fourth set featured some superb tennis, with Alcaraz unveiling his drop-shot and Zverev scrambling magnificently.

Then an Alcaraz double-fault handed Zverev a break and the chance to serve for the match.

But Alcaraz took on the challenge, forcing three break-back points and taking the second to level at 5-5.

Both players subsequently held serve before Zverev sealed the match in the breaker.

with AAP

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