Djokovic double faults, but he follows up a blistering serve out wide with a forehand to draw level once again.

The crowd heckle one of their own who fails to catch a wayward ball into the stands. That came from the racquet of Nishikori, and another Djokovic service game appears to be getting away from him...

Nishikori takes charge on serve as he leaps into a forehand winner for 30-15. Djokovic comes roaring back with a fizzing return for 40-30, but it's the world number 56 who delivers the final blow with a backhand and we remain on serve in the fourth.

The crowd, willing a fifth set, cheer as Djokovic nets and Nishikori gets up and running at 30-15.

But, as we move past the three-hour mark in this contest, Djokovic closes out to hold.

Well played. Nishikori keeps his cool and some good serving ensures there'll be no early set-back.

Can Kei Nishikori force a fifth set? It's what the Arthur Ashe crowd want, but will Novak Djokovic allow it...

The world number one has a break point at the start of the fourth.

Yep, I'm still thinking about that Raducanu win too.

This is a nice graphic, if you're into that kind of thing.

That means a lot to Novak Djokovic.

The world number one battles his way to the third set against an in-form Kei Nishikori.

It's been a struggle, but he's turned it around and now the fourth round is in sight.

A huge roar from Djokovic as the Serb blasts a backhand down the line for 30-0. The third set is within reach.

Djokovic forces the mistake from Nishikori for break point...

Gets it! Djokovic breaks. Champion response.

Djokovic, seeking an immediate response to that set-back, lifts long when leading 15-30.

More good work from Nishikori sees the world number one net but the Japanese player can't make it four points on the spin. Deuce.

Right then, time for us to rejoin the action on Arthur Ashe.

Novak Djokovic lost the first set in a tie-break against Kei Nishikori, but bounced back to claim the second.

Now, in set three, Djokovic had led by a break but Nishikori has just battled back from 40-0 down to break back! Game on.

The performance of the 2021 US Open so far? Quite possibly.

Image source, Getty Images

Here is what Emma Raducanu had to say in her post-match interview:

"I was playing very well and I know Sara is an extremely tough opponent. I had to work so hard and there were some really long deuce games that could have gone either way. I'm just very glad I was able to maintain it and win in the end.

"For this one the plan was I had to hit through her and into the corners. I just took the game to her and I hit more winners than errors today.

"I have a great team around me. We're sticking to the same routines. I never thought I'd be here but I'm so, so excited. I'll recover tomorrow and then back on it on Monday.

"Honestly the crowd is so amazing so I want to thank absolutely everyone. Thank you so much. they have helped me through so many moments."

Laura Robson
Former British number one on BBC Radio 5 Live Sports Extra

I can't believe what I've seen. She did not let up, she wanted to win 6-0 6-0 and she wanted it to be an absolute beatdown. And it was.

Emma Raducanu is still out on court signing autographs. She's refusing to leave anyone disappointed!

She's already a real fan favourite at Flushing Meadows.

It could, very likely, be world number one Ashleigh Barty in the last 16 for Emma Raducanu.

And as Joel points out, even if American Shelby Rogers springs a shock there's still a high chance the match is played on Arthur Ashe Stadium.

What an experience that will be for the teenager, whoever she faces.

Stash: Words fail me and I have watched a lot of top tennis and played a bit as well That was just outrageous from Emma Raducanu - 18 years old with almost no experience at this level.

Sho: The most one-sided match I've ever seen, men or women. Absolute beat down from Raducanu.

Joel Newnham: That was awesome from Raducanu but her next challenge will be so different against world number 1 or crowd favourite so without a doubt on Ashe. I can't wait

Laura Robson
Former British number one on BBC Radio 5 Live Sports Extra

We kept bigging this match up as such a tough opponent, and Sorribes Tormo is. She has the game to get you in trouble but she never had a chance to play her game. Emma came out and hit her off the court. It is just incredible, the way she was able to tactically play today. It never felt like it was too much for her. It's an unbelievably impressive performance from such a young player. She now has nothing to lose against, potentially, Ash Barty.