David Law
BBC Radio 5 live sports extra commentator at Flushing Meadows

Every point now is punctuated with Andy Murray saying things in the direction of his coaching team - I'm not sure what, but lots of things...

I wonder if he's feeling it physically? Whether his legs are not quite doing what he's asking them to do? How much energy does he have left in the tank?

He suddenly looks absolutely exhausted, a bit down in the dumps.

Dusan Lajovic is having another medical timeout before the fourth set begins, it looks like he's having some talc applied to his feet - blisters for the world number 62?

Murray opens up half of his big wingspan and swats away a forehand.

Advantage.

He then makes an overhead.

Game.

Much needed for Murray.

David Law
BBC Radio 5 live sports extra commentator at Flushing Meadows

Fernando Verdasco jumped in a bit prematurely there.

Verdasco started the fourth set on fire, but Murray has fought back now. Murray is now the world number 382 - the British number eight.

Verdasco goes for a challenge mid-rally - big call at 30-30.

It was in by quite a bit. Relatively speaking.

Bad call Fernando. 40-30.

Murray then goes wide.

Deuce.

Jonathan Jurejko
BBC Sport at Flushing Meadows

Andy Murray is not a happy camper when he returns to the court.

He tells the umpire he's back early after seeing Fernando Verdasco in there chatting to members of his team. That is not allowed under the extreme heat rule.

"It is because no-one knows the rules," says Murray, possibly adding in an expletive. (He definitely swore for added emphasis.)

Murray apparently suggested to the umpire that Verdasco was talking to his team in the locker room which he wasn't supposed to during the Extreme Heat Policy break.

Hmm...

Anyway, 15-30.

Murray is keen to get on with it.

Verdasco is doing his laces.

British number two Cameron Norrie has just lost the third set to Serbia's Dusan Lajovic.

Let's hope the 23-year-old is geared up for a five-setter, because that's what it's going to take if he is to turn this second round match around...

Promise it's not just us Brits who are moaning about the heat. Even the locals are struggling to cope.

Vivien Lee and Ben Wood are from New York City and even they say this heat is extreme.

"I've been coming to the US Open since I was about eight years old - it is probably the hottest one I've ever been to," says Vivien.

"We've drank two gallons of water and put on sunscreen three times now. Parasol, portable fan, sunglasses, hat.. we're ready to.

"And plenty of money for water - and beer."

Image source, BBC Sport

While Vivien and her friend Ben can move off court whenever they want, the players - extreme heat breaks aside - aren't so lucky.

"We saw Stefanos Tsitsipas on court 10 earlier - he was definitely struggling," Vivien added.

Ben, who is from Texas, has a good - if not costly - solution. "They should build a roof on every court - with air conditioning," he jokes.

"This is so much worse than Texas because everywhere has a roof with air conditioning.

Jonathan Jurejko
BBC Sport at Flushing Meadows

"Do you want 10 minutes?" umpire Nico Helwerth asks Verdasco. That'll be a 'yes'.

Murray stays in his chair before being told that the break is happening. Only one of the players need to want the extreme heat rule enforced for it to happen.

The Scot grabs his bag and trudges off after Verdasco. Presumably, judging by Novak Djokovic's comments yesterday, they are going to see a bit more of each other in the adjacent ice baths...

Did Murray sarcastically applaud his corner there?

He then asks the umpire, somewhat flustered, whether the 10-minute heat break had begun.

It had.

The players go off for a cuppa and cake. Maybe.

40-30.

Verdasco clinches the set with conviction aka a powerful double-handed backhand approach.

Gutsy from the Spaniard.

Jonathan Jurejko
BBC Sport at Flushing Meadows

Murray might have been out of the spotlight for a while, but he remains as popular as ever.

The Ashe crowd is whooping and hollering as they try to will him into nabbing a break to save the set.

The Scot makes another error - his 10th of the set.

30-15.

Verdasco can't pick up a volley from Murray at the net as the ball reaches the umpire.

30-30. Tense times in the Verdasco camp.

Dom Inglot
British doubles player on BBC Radio 5 live sports extra

The key for Verdasco here is a good first serve percentage and making sure he's not too erratic on the forehand.

Murray knows this is the time to break the spirit of Verdasco. If he can get a break, suddenly everything changes.

Good start for Verdasco with a shot down the line

He's won 70% of points on his first serve in this set.

Murray bites back by coming to the net and smashing one down and beyond.

15-15.

30-0.

Murray then decides Verdasco will win the next point, which he does.

30-15.

The Scot produces huge forehand winner from the back.

40-15.

Game.

He must now break Verdasco.

Wimbledon finalist Kevin Anderson has won the opening set of his second round match against France's Jeremy Chardy.

The South African fifth seed won 80% of his first serve points, but was surprisingly out aced by Chardy in that opener - 4-5.

Cat Archer
BBC Radio tennis producer on Arthur Ashe Stadium

Both Andy Murray and Cameron Norrie’s matches will soon be eligible for the 10 minute heat rule break.

Yesterday Djokovic and Fucsovics had a quick cold dip together during theirs. Only issue is...there are only two ice baths in the locker rooms (as demonstrated here by Pablo Carreño Busta).

Dom Inglot just assured us on 5 live Sports Extra you can’t fit two people in one - so is it first come first serve?

Image source, Pablo Carreño Busta