Jill Craybas
Former world number 39 on BBC Radio 5 live sports extra

Nishikori just needs to be like 'I know I am playing well' and focus on what he is doing. He is playing really well. It is such a high-quality match.

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

It must be horrible to hit your very best shots at somebody and for it to have no impact.

Well done Kei Nishikori! Finally he wriggles free after 14 minutes. A little fist pump from the Japanese 21st seed. The crowd are starting to side with him as they hope for their money's worth.

The bad news is all that effort was only worth one game.

Will this game ever end?! Over 12 minutes now. Deuce number six...

Now the frustration is showing from Djokovic. He misses the break point chance again and chunters away to himself. He wants this break bad.

This game has been going nine minutes now. Nishikori wipes the sweat away from his eyes with his purple sweatband after fighting off the break point. But he's going to have to do it again...

Jill Craybas
Former world number 39 on BBC Radio 5 live sports extra

Djokovic wears you down and makes you feel like you have to go for broke. Nishikori has.

Djokovic is showing little emotion on court. He looks completely focused.

Break point again.

Nishikori pumps his fist not once but twice after fighting off that break point. He's still got work to do to get out of this game however.

Deuce.

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

I have not seen any better tennis than the first points of this second set. They are hitting it fine and true! If Nishikori drops serve here, he is going to be absolutely devastated! The crowd are engrossed in the drama. Nishikori is playing brilliant tennis!

How has he hit that?! Brilliant from Kei Nishikori. He's on the run again but gets out his extendo-arms and flicks a sliced drop shot cross court.

But Djokovic responds! A thumping backhand winner.

Break point Djokovic. What a game!

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

Nishikori has thrown the kitchen sink at Djokovic in those last two points! He'd have beaten anyone in the world on those points except Djokovic.

Wowser. That's some rally. Both players pound away at each other but once again Djokovic has the answer. Nishikori must be wondering what he has to do to win a cheap point.

0-30.

Jonathan Jurejko
BBC Sport at Flushing Meadows

Ouch! Groans of sympathy ring out around Ashe as Nishikori buckles when landing awkwardly.

Nishikori has a rich history of retiring injured. Let's hope we don't get another after Nadal's demise earlier.

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

Djokovic made quick work of that much to the delight of his trainers. They were standing up and cheering as if that first set meant a lot more than we thought it would. I still think Nishikori is a little beat up from the last match. He just doesn't look that solid physically.

Novak hit just four winners in that set and Nishikori six but that doesn't tell the story at all.

Nishikori didn't really land a punch.

Russell Fuller
BBC tennis correspondent on 5 live sports extra at Flushing Meadows

Djokovic was very much in command.

Well that's as comfortable first set as you could hope for in a Grand Slam semi-final.

Djokovic wraps it up with an ace. All over in 37 minutes.

Kei Nishikori must break or he'll fall a set behind...

Imposing start from Novak. 30-0.

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

It was a mumble, stumble and a fumble into the hold!