'It's fun': Alcaraz steals Djokovic play at the Open

Later on Sunday, world No.3 Alexander Zverev sealed his own quarter-final berth with a 6-2 6-4 6-4 win over 18th seed Francisco Cerundolo.

So often looking on the back foot, Alcaraz broke Paul's serve - and the world No.20's heart - when it mattered most in cruising, like only he can, into his 14th grand slam quarter-final.

The six-time grand slam champion had no real right to win the opening set after his start, before clinically dismantling Paul to advance to a last-eight showdown with sixth-seeded home hope Alex de Minaur or Kazakhstan's world No.10 Alexander Bublik.

After dropping serve in the opening game of the match, Alcaraz had to work overtime to break back into the first set.

Paul had not dropped serve all tournament, holding for 38 consecutive games.

But he had not faced the world's No.1 player either.

Refusing to yield, the super Spaniard rallied back from 4-2 down, then a mini break in the tiebreaker, to snatch the set on a Paul double-fault following a 12-minute disruption to remove an ailing spectator from RLA.

While the scoreboard displayed more of a contest, Alcaraz controlled the second and third sets to prevail in two hours and 44 minutes.

"He started pretty strong in the first game," Alcaraz said.

"I thought I just played a good game, though, but he came with a really strong shot, really flat, so it was difficult for me.

"But I stayed there all the time. Overall it's been a really high level of tennis from both sides.

"Really happy that I got it in straight sets."

Still only 22, Alcaraz has one last chance to eclipse American Don Budge as the youngest man ever to complete a career grand slam.

The two-time Wimbledon, French and US Open champion conceded he was only too happy to tinker with his service action to complete the slam, even if it meant mimicking his great rival Djokovic.

"To be honest, I wasn't aware that it was really similar to Nole's," Alcaraz said.

"Novak's like 'Wait, that's my serve. He's gonna have to pay me some money for that serve.'

"I heard that. I have the contract over there but I haven't seen him yet.

"I just woke up and I took out my phone and had, you know, a Djokovic message.

"Like, 'All right, you have to pay me for the serve before the season'.

"Yeah, yeah, he sent me the message, so it was fun.

"I mean, these kind of things in the locker, it's fun to share with another player.

"It's especially fun when it works out and you're serving better."

De Minaur and Bublik play the feature night match on RLA on Sunday.

On Sunday afternoon, Zverev, who is still seeking his first slam title, cruised into the last 16 with his straight-sets win over Cerundolo.

"Very happy with the match," Zverev said.

"He's a high-quality player - didn't lose a set before this match here in this tournament.

"Really happy with the performance and really happy to be back in the quarter-finals."

When asked if he was playing his best tennis, Zverev said: "I don't wanna jinx it so I'm gonna keep my mouth shut."

Zverev will play the winner of Sunday evening's match between three-time Open finalist, 11th seed Daniil Medvedev, and 25th seed Learner Tien.