Jannik Sinner seems determined to give it a go but mishits an overhead on the very first point of the deciding set. Is that an omen?

A long rally finishes with a Sinner error and he then undercooks a drop shot to give Cerundolo an early chance to break.

Sinner is coming to the net when he can now to shorten the points - and even manages to find the energy for fist pump after putting away a volley.

But Cerundolo is chasing everything down and earns the early break.

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra

I just didn't see this scenario happening, no one knew it was going to be this hot, this sweltering, these brutal conditions and I think we underestimate how much it takes out of them. Being out there in this climate is like being in a cauldron or an oven.

Image source, Getty Images

Worth emphasising again that Jannik Sinner entered the French Open as one of the most overwhelming favourites to win a men's Grand Slam in recent times.

His big rival Carlos Alcaraz, the defending champion, is missing the event with a wrist injury.

Sinner had won 37 of 39 matches in 2026 before this one, has lifted plenty of titles and he has not lost since a defeat by Jakub Mensik in Doha in mid-February.

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra

This is not the first time that I have seen Sinner with nothing left in the tank and then suddenly he will find something when it matters.

Image source, Getty Images

Juan Manuel Cerundolo enjoys a comfortable hold of serve, and we are going into a fifth and deciding set.

Jannik Sinner's box are trying to encourage him but the world number one is still really struggling.

A couple of incredibly slow second serves give Juan Manuel Cerundolo another chance to break - and the Argentine player does just that.

Cerundolo will now serve for the fourth set.

Jannik Sinner is trying to keep the points short and blasts a couple of winners to go 0-40 up.

But Juan Manuel Cerundolo knows he has to keep Sinner on the move, and wins the next five points by doing just that.

Even walking is a struggle for Sinner again at the moment.

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra

Sinner went for a quick point and got the smash away and he couldn't even celebrate that, he is just weary. I feel like we are watching someone in the desert.

Image source, Getty Images

Jannik Sinner is really digging deep here but it might not be enough.

A forehand clips the net and lands out, to leave him facing two break points.

And Juan Manuel Cerundolo clinches the break by chasing down a Sinner drop shot and putting it out of the Italian's reach at the back of the court.

BBC Radio 5 Sports Extra

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Somehow, Jannik Sinner carves out a break point and then goes for broke when returning Juan Manuel Cerundolo's serve but his forehand finds the net.

Cerundolo then saves another break point with a brilliant lob, which leaves Sinner bent double at the back of the court.

It's hard for the Argentine, who has to try to make Sinner move but also keep his focus, but he manages to hold.

Image source, Getty Images

Jannik Sinner has had his issues with playing in extreme heat before.

At the Australian Open in January, he said he "got lucky with the heat rule" after coming through a third-round match with Eliot Spizzirri on a day the temperature got close to 40C in Melbourne.

The Italian was visibly struggling with cramp just before the heat rule was enforced, with play delayed while the roof over Rod Laver Arena was closed and the air conditioning took effect to cool the stadium.

Jannik Sinner wins his first game since going 5-1 up in the second set.

The Italian clearly wants to keep these rallies short - a drop shot is followed by a ferocious winner down the line.

He is still leaning on his racquet between points but maybe there are signs that he can play his way through this.

Earlier in the tournament, BBC Sport's Jonathan Jurejko wrote about how players are coping with the hot conditions at Roland Garros.

Jannik Sinner's 30-match unbeaten streak is under threat here.

The world number one looks laboured - he hits a forehand winner but then leans over on his racquet afterwards.

He looks like he can't move.

Juan Manuel Cerundolo is keeping his focus and takes the first game.

Jannik Sinner is not the only player to struggle with the intense heat at this year's French Open.

Yesterday, Jakub Mensik collapsed on court with cramp immediately after completing a second-round win against Mariano Navone, which lasted four hours and 41 minutes, and said afterwards that his body "just turned off".

Earlier in the week, Casper Ruud said he felt he was "walking around like a zombie almost" during his first-round win at the temperature reached 33C.

Image source, Getty Images

After losing 11 straight points, Jannik Sinner called for the trainer at 5-4 down in the third set with Juan Martin Cerundolo in possession of three break points.

Sinner had appeared laboured with a dejected expression on court, and he told the trainer he felt “dizzy” and “felt like vomiting”.

After a time-out, Sinner returned to the court but still appeared weary as Cerundolo went on the win the third set 7-5.

No surprise as Juan Manuel Cerundolo takes the third set.

Jannik Sinner goes off court again but returns for the fourth set.

Is there any way back for him from here?

Jannik Sinner's struggles started midway through the third set.

At 5-4 up, he spoke to the umpire on court, consulted with the trainer and was assessed off court.

After that, he lost the next three games and the world number one now leads by two sets to one.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Welcome to day five of the French Open - and it's already looking like it could be a dramatic one.

World number one Jannik Sinner was first up on Court Philippe-Chatrier and was cruising to victory against Juan Manuel Cerundolo of Argentina.

But after taking the first two sets comfortably, the Italian looks to be struggling in the hot conditions of Paris.

From 5-1 up in the third set, he has completely fallen away and has just lost the third set.