Nadal is placing his drinks in a particular order, as he always does, and lines his kit up in a very organised manner.

A few photos are snapped and the umpire says a few things. Nadal is jumping up and down and Del Potro is swinging his racquet from side-to-side.

A quick shuttle sprint from both players towards the baseline and the warm-up begins.

Chanda Rubin
American former world number six at Flushing Meadows

Nadal has had knee issues in the past. I think he manages those issues well. He is smarter how he plays the points. How much he is able to do that will be the key.

The music has been turned up. The crowd are roaring. The giants are out.

Jonathan Jurejko
BBC Sport at Flushing Meadows

No prizes for guessing who this lot are supporting tonight...

Image source, BBC Sport

A bunch of animated Argentines are gathered behind a television presenter as she delivers a live broadcast from outside Ashe back home.

After doing her piece to camera, she canvasses the crowd for their opinions on how Del Potro will fare.

"Gana!" they all shout in unison.

That, if my limited Spanish is correct, means 'Win!'

One bloke reckons it'll be in four, another in three because he thinks Nadal will struggle physically after some gruelling matches in the earlier rounds.

They then break into a chant. "Ole, ole, ole, ole, Delpo, Delpo!" as they jump around for the cameras.

Textbook television.

Chanda Rubin
American former world number six at Flushing Meadows

Juan Martin del Potro is a different player and I think he is playing even better tennis than he played back in 2009 when won the title.

He has adjusted his game and is a smarter player.

This match-up has been to Nadal's favour but when you consider the battles they have had, this should be a special match.

The pair's meeting at Wimbledon in the quarter-finals lasted almost five hours with Nadal winning a thrilling fifth set.

And Del Potro is expecting a similar battle this evening.

"It could be another big battle, as the Wimbledon match was," Del Potro said.

"Of course, I like to play always with the number one of the world, it doesn't matter the tournament or the conditions.

"I just have the chance to play the greatest in this sport, and it's amazing for me."

Image source, Getty Images

Chanda Rubin
American former world number six at Flushing Meadows

I'm excited.

Jonathan Jurejko
BBC Sport at Flushing Meadows

While the rowdy Argentines are getting most of the attention outside Ashe, there are plenty of their Spanish counterparts knocking around.

If the Spanish flag isn't a give away then the logo of the Nadal bull on the baseball caps worn by Alberto Nogueira, Alberto Nogueria (senior), Michelle Palmeirez Jose Yaber sure is.

Image source, BBC Sport

"We are here in New York for business and fun - this is the fun!" laughs Alberto senior, who has crossed the Atlantic from the city of Santiago de Compostela in northern Spain

"We are always watching him on television and this year we made the decision to so something special because we work very hard.

"So we said 'let's go to the US Open semi-finals and final'. This is the first time we have seen him live so we are very excited."

But will they see in the final? "Of course. It will hard but he will win. I'm sure."

Nadal and Del Potro have met twice in Grand Slams this year, at the French Open and Wimbledon, with Nadal winning on both occasions.

But the world number one has spent nearly four hours longer on court than Del Potro at Flushing Meadows, including a gruelling four-hour 49-minute marathon against Dominic Thiem in the quarter-finals.

"It will be a very tough one," three-time US Open winner Nadal said.

"At Wimbledon he's a great player, he's a great player everywhere. But the challenge of playing him on hard courts, of course, is even higher for me personally.

"I know that I will have to play at my highest level to keep having chances of success. I am focused on trying to make that happen."

Former champions Rafael Nadal and Novak Djokovic will bid to set up a 53rd meeting when they take to the stage in their opposing semi-finals this evening.

The pair have met more than any two men in the Open era and could meet for a fourth time in the final in New York.

Defending champion Nadal faces Argentine third seed Juan Martin del Potro and is aiming for an 18th Grand Slam title.

Two-time winner Djokovic follows against Japan's Kei Nishikori and is looking for back-to-back Grand Slam titles following success at Wimbledon.

Image source, Getty Images

This is it. A place in the US Open final is up for grabs!

First up it's the reigning champion and French Open winner Rafael Nadal against 2009 US Open champion Juan Martin Del Potro.

Then it's the Wimbledon champion Novak Djokovic against 2014 US Open runner-up Kei Nishikori.

Grab a brew, open a pack of biscuits and set yourself up for the night. This is going to be EPIC.

Image source, Getty Images