David Law
Commentator on BBC Radio 5 Sports Extra

It seems there is a new-found focus and maturity in the way Alcaraz is playing in this tournament - the shaved head, the attitude of desperately wanting to be consistent.

He looks on it. He has hit a few long, but the more balls he hits and the more tension he gets out of the body, the less likely he is to hit long.

A gruelling start for Djokovic as Alcaraz gets the break in the very first game when the Serb can't keep the ball inside the lines.

There's already so much quality on display here. Alcaraz brings up another break point.

Djokovic stands and stares in frustration.

Alcaraz drives up to the net to try and catch Djokovic off guard but it's sublime defence from the 24-time major champion to fend off that aggression and Alcaraz's backhand volley ends up in the net.

Break point saved.

Not the easiest of service games for Djokovic to get this started.

A fast start from second seed Alcaraz brings up break point.

Off we go then. Strap in, folks.

* denotes next server

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Spot the odd one out?

Three of today's semi-finalists already have their names etched on the US Open's champions' board...

Image source, BBC Sport

We've seen unusual celebrations from both players at this tournament.

Carlos Alcaraz, sporting that new hair do, has mimicked a golf swing with every win in New York. The Spaniard plays a lot of golf in his downtime and is friendly with a lot of the pros, dedicating one early-round win to Rory McIlroy.

Image source, Getty Images

For Novak Djokovic, his runs at Grand Slams are often celebrated in novel ways, usually along the lines of something to do with his children.

At Wimbledon we saw a special dance to 'pump it up' and here in New York it's also dancing we've seen, inspired by the film K Pop Demon Hunters and dedicated to his daughter.

Image source, Getty Images

One thing we can definitely say is that time is not on Novak Djokovic's side when it comes to taking the standalone major titles record.

The Serb already tapers his training and manages his competition time to make sure he is in peak condition at the Grand Slams, missing out on many other Tour events to focus on the majors.

But, as we saw at Wimbledon, the 38-year-old dropped off in week two of the tournament and ultimately ran out of steam when he faced Jannik Sinner in the semi-final.

And here in New York we have seen him frequently taking medical timeouts during matches.

How many more opportunities will Djokovic get? Particularly when he knows that at some point or another he will have to face the likes of Sinner and Carlos Alcaraz to win another Slam.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Image source, BBC Sport

The world-famous Yankees are starting their weekend series against the Blue Jays.

Throwback folk-popper Benson Boone is stepping out at Madison Square Garden.

Star power In NYC today.

But they aren't Novak Djokovic and Carlos Alcaraz hitting Arthur Ashe Stadium in the US Open semi-finals.

Maybe I'm biased but this feels like the hottest ticket in town today.

Thousands of fans waited patiently as they shuffled towards the gates when they opened about half an hour ago.

Bohemian Rhapsody star Rami Malek probably hit the express lane.

Image source, Getty Images

The players are out and warming up. What an atmosphere building in New York.

Carlos Alcaraz has defeated Novak Djokovic in two Wimbledon finals, but Djokovic has been triumphant in their last two meetings - including at last summer's Olympic final.

BBC Radio 5 Live Sports Extra

You can listen to live radio commentary from BBC Radio 5 Live at Flushing Meadows by clicking the play icon at the top of this page.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Third-wheeling is nothing new to Novak Djokovic.

When the 38-year-old first emerged as a force in the late 2000s, he was the outsider looking to break up the cosy coupling of Roger Federer and Rafael Nadal.

Nearly 20 years later, Djokovic again finds himself squeezed out at the top of the men's game.

If Djokovic is going to defy expectation - and logic - by winning the US Open title, he will have to beat second seed Carlos Alcaraz in Friday's semi-finals and then possibly top seed Jannik Sinner in Sunday's showpiece.

"Everybody is probably expecting and anticipating the final between the two of them," said Djokovic, who has reached the semi-finals at all four majors this year.

"I'm going to try to mess up the plans of most of the people."

Novak Djokovic remains in pursuit of a standalone record 25th Grand Slam singles title.

I know, I know - we talk about it a lot. But for a long time it looked like a given that that record would eventually belong to him and now that idea has slowly begun to slip away.

As Djokovic gets older his ability to hang in there in the majors and beat youngsters like Jannik Sinner and Carlos Alcaraz lessens.

The hard courts are where Djokovic has enjoyed most of his success - can he get it done just one more time?

Let's be honest, it's the match we all hoped for when the tournament began.

A blockbuster semi-final between veteran Novak Djokovic and young superstar Carlos Alcaraz.

Will it be a first US Open final since 2023 for Djokovic? Or first since 2022 for Alcaraz?

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Image source, BBC Sport

Things are heating up in New York.

Metaphorically as we move into finals weekend. And literally as the heat and humidity returns in the Big Apple.

This year’s US Open has largely been held in cooler, fresher conditions, but today’s first men’s semi-final will be played in stuffier air.

That, one would imagine, should lead to advantage for Alcaraz, who is younger, fitter and grew up playing in parched southern Spain.

Image source, BBC Sport

Right, a superb night of tennis ahead. Get your coffee, get your snacks. Here's what's coming up...

First up, for a place in the final in New York, 2022 US Open winner Carlos Alcaraz takes on 24-time major winner Novak Djokovic on Arthur Ashe.

Then world number one Jannik Sinner will face the tournament's surprise package in Canadian Felix Auger-Aliassime as he aims to defend the title he won 12 months ago.

The 2025 US Open women's final line-up is complete.

Now it's over to the men. And boy have we got a couple of crackers lined up this evening.

Image source, Getty Images

Image source, Getty Images