Joao Fonseca is hitting the ball so hard.

The young Brazilian holds again, securing the game with a ferocious forehand, followed by an even more ferocious roar.

After some lung-busting rallies in the previous game, Novak Djokovic will be pleased to hold with four quick points.

The match-time has just turned two hours.

Annabel Croft
Former British number one on BBC Radio 5 Live

This crowd are being treated to something different every single match. This is absolutely jaw-dropping what we are witnessing here.

Image source, Getty Images

This is a really crucial stage of the match, and Joao Fonseca holds his nerve amid some brilliant rallies.

Novak Djokovic gestures agitatedly to his box. He will know all too well that he was cruising in his second-round match until the third set.

Fonseca has his chances to put the game to bed but Djokovic also manages to carve out break chances.

There's another brilliant rally, where Djokovic shows amazing defence before netting as he tries to turn it into attack.

Another chance to break comes and goes, and after Djokovic shanks a smash, Fonseca finally clinches the game when Djokovic nets after another breathtaking exchange.

Annabel Croft
Former British number one on BBC Radio 5 Live

You can tell from Djokovic's body language that he is wound up.

Credit to Joao Fonseca, he's not giving up - and he gets his reward with a break!

The teenager moves Novak Djokovic around the court before unleashing a blistering forehand into the back corner of the court.

He then capitalises on break point when Djokovic finds the net.

Is there a change of momentum here?

Annabel Croft
Former British number one on BBC Radio 5 Live

Djokovic is drawing upon every ounce of his experience here and he has to.

Novak Djokovic may be two sets up but he's not happy with the camera operator who he feels is encroaching on his space at the changeover - "Can you come more in my face?" he asks sarcastically.

Joao Fonseca keeps his focus to hold at the start of the fourth set.

Annabel Croft
Former British number one on BBC Radio 5 Live

Another really special point from both of them. It is incredible to see this live from Fonseca, it is like a boxer putting in a huge point.

Image source, EPA

Over on Court Suzanne-Lenglen Ukrainian eighth seed Elina Svitolina has won the first set 6-2 against unseeded German Tamara Korpatsch.

In the men's draw, there's a potential surprise brewing on court 14 with unseeded Dutchman Jesper de Jong taking the first set 7-5 against Russian 13th seed Karen Khachanov.

Image source, Getty Images

Once again Novak Djokovic concedes the first point of his service game.

But this time, he bounces straight back, and a brilliant long rally, which ends with Djokovic blasting the ball croos court for a winner, gives him two set points and has him cupping his ear to the crowd.

He takes the next point much more easily to take a two-set lead.

Annabel Croft
Former British number one on BBC Radio 5 Live

It feels like Djokovic is incredibly stressed and Fonseca is causing that stress.

An impressive service game from Joao Fonseca.

But now the 19-year-old needs to find a way to break Novak Djokovic, who will be serving for the set.

Rafael Jodar gets right back on track by breaking back but can he consolidate it?

The Spaniard's service game goes to deuce but Jodar keeps his composure by ending a seven-shot rally by cracking a winner past Alex Michelsen.

Jodar is potentially one game away from the last 16.

Annabel Croft
Former British number one on BBC Radio 5 Live

That is vintage Djokovic on that last point, in lockdown, not trying to do anything, just a wall of steal saying 'I am not going to do anything'. I think he just let out an enormous amount of stress that he was carrying in that last game.

Image source, Reuters

Novak Djokovic saves the break point with a big first serve.

And then another big serve secures the hold.

Joao Fonseca must now serve to stay in the second set.

Novak Djokovic hits a rare loose forehand and then fails to put away a drive volley, and suddenly the glimpse of a chance for Joao Fonseca at 0-30 up on Djokovic's serve.

And Djokovic then nets to give break point to Fonseca.

Joao Fonseca decides to change his racquet - and it does the trick, as he holds to love.

But the 19-year-old is still down in the set - he needs to break Novak Djokovic.

We've just hit the four-hour mark and all of a sudden, Alex Michelsen springs into life and arrows a backhand winner across court for two break points.

He might not be playing to his full potential with some reported back problems, but the American bites down and secures the break.

Whose match is it from here?