Jonathan Jurejko
BBC Sport at Flushing Meadows

Image source, BBC Sport

While Serena Williams and Maria Sharapova had everyone reaching for the popcorn because of their previous, this feels like a bigger deal tonight.

Outside Ashe is a square packed full of excitable fans, most munching sandwiches filled with steak and onions, or mustard-topped hot dogs, swilling them down with cold Dutch lager.

Whoops greet Boris Becker pulling out his phone for a selfie on the Eurosport set from the tens of fans lurking behind him with their camera phones, similar excitement as Pam Shriver does a live take on ESPN.

Image source, BBC Sport

Swiss 13th seed Belinda Bencic.

She was given a walkover after Estonian opponent Anett Kontaveit retired with illness before their match on Louis Armstrong today.

It is Bencic's first appearance in the US Open second week since she made the quarter-finals as a 17-year-old in her tournament debut in 2014.

Image source, Getty Images

Jonathan Jurejko
BBC Sport at Flushing Meadows

Asking people walking into Ashe who they are supporting is getting me some funny looks.

One woman steps back, gives me a sassy stare and asks who I think she is supporting.

“Erm, Coco?”

“Hell yeah, she’s our girl!”

Naomi Osaka might have New York heritage but, like she was in last year’s final against Serena Williams, will be facing the crowd as well as Gauff.

“She dealt with it last year, so she’ll be fine,” adds the lucky ticket holder.

There was some suggestion Osaka’s name was booed by the Armstrong crowd during Gauff’s on-court interview after her last win.

One to keep an ear out for...

It is only 15-year-old Coco Gauff's second appearance in a Grand Slam singles main draw, after she reached the fourth round at Wimbledon before losing to eventual champion Simona Halep.

Serena Williams says this tie is a match-up of the "future of women's tennis", while Coco also received praise from five-time US Open champion Roger Federer.

"She's [Coco] done so well again here this tournament," said Federer. "I think we're all a bit surprised that she's able to back it up after Wimbledon which was already an incredible run.

"For her to strive in those conditions shows she's going to have a great future ahead of her. It's going to be a big day [on Saturday]. I wish her all the best, of course."

Jonathan Jurejko
BBC Sport at Flushing Meadows

Image source, BBC Sport

This is the view as you wander into the Billie Jean King Tennis Centre from the East Gate, the entrance which serves the Mets-Willets Point subway and rail stations linking Flushing Meadows to midtown Manhattan.

Around 6pm local time (an hour before Gauff and Osaka walked out on to Ashe), the place is packed with punters wandering around in the evening sun and sipping on a Honey Deuce.

That's the US Open's trademark drink - fresh lemonade spiked with vodka and a hint of raspberry liqueur. Not to forget the melon garnish.

It's nice. But it's not Pimms.

Even Serena Williams is excited for this one.

Defending champion Naomi Osaka takes on teenage sensation Coco Gauff, playing in front of a home crowd on Arthur Ashe.

Japanese top seed Osaka, who beat Williams in the final last year, also won the Australian Open in January but hasn't been in great form since.

She reached just the third round at the French Open before being knocked out at the first stage at Wimbledon and has also failed to beat a top-10-ranked player since the start of the year.

Meanwhile, Gauff has continued her impressive form, winning her first WTA doubles title at the Washington Open alongside compatriot Catherine McNally.

Image source, Getty Images

Right, we are going to take a breather and come back for tonight's big clash between world number one and defending champion Naomi Osaka and 15-year-old superstar Coco Gauff.

See you then...

Here is Rafael Nadal, on opponent Chung Hyeon: "When he is healthy he showed to everyone how good he is, playing the semi-finals in Australia. He had injuries and I know by personal experience how tough it is. I am very happy for him. He went from the qualifier and won two matches in five sets, I wish him a healthy career and all the best."

On his injuries: "Tape is not working anymore... I am happy to be playing on hard court. I am trying to play a little bit more aggressive, a little bit less than before as everyone can see I missed Miami for an injury and I was sad because I want to play everywhere but I am not 25 anymore.

"Here I am, happy to be in the fourth round. This court is unique, it's so special the energy the crowd brings to this scenario.

"You never know what is better or worse, I have a tough opponent in front of me - Marin Cilic or John Isner - I can't think further than this. I think day by day."

On his purple outfit: "It took me a lot of hours to pick... joking, we choose the colours but for one year and a half in advance! By the time the tournament arrives I already forget what I chose. I like happy colours."

Alexander Zverev is back in it. He's taken the second-set tie-break. This one is going to go to the wire isn't it?

Quick towel down for Rafa. Off comes the purple vest, on goes the purple jacket.

Fresh baseball cap donned, now we're good to talk...

Britain's Dan Evans and Cameron Norrie are going to have to play a third set. Each pair broke back on two occasions before the British pair fought off two set points.

They couldn't fight off a third though, with the top seeds finally getting a breakthrough.

Can the British pair recover to win the decider?

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

Nadal cruised through the second set then turned it up a little bit in the third set. There was never a fifth gear that was needed.

Another massive forehand winner from the Spaniard and that's two match points.

Big, big second serve from Rafael Nadal. He nods in delight. 30-15.

Rafael Nadal just creaks through the gears and scuttles forward to slap away a punchy forehand winner. 15-15.

Hello! What a passing backhand winner from Chung Hyeon. He's hanging in there..

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

Nadal looks very comfortable. He has stayed in third gear and hasn't had to extend himself. These are perfect conditions to play in. He will be happy with what is going on and will already be looking forward to the next match.

And the Spaniard does get the double break. This one is quickly slipping away from Chung Hyeon. Rafael Nadal will serve for the match.

Make that two break points for Rafa...