A huge forehand from Nishikori draws a mistake from his opponent and the 10th seed is closing in on the third set. He then challenges a point that was called out, and that takes us to a second deuce.

Nishikori then has a set point, before slapping his shot into the net, and Wawrinka recovers to hold his serve on a hot and sweaty day at Flushing Meadows. But Nishikori is now serving to move into a 2-1 overall lead.

Nishikori has come alive now. There's more aggression in his strokes as Wawrinka grows increasingly frustrated.

A Wawrinka return goes long for 40-30 and Nishikori sends down a fierce first serve to take the game.

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Two break points for Nishikori at 15-40, with Wawrinka still unsettled after losing that second set.

He puts away a short one from Wawrinka to take the first opportunity and breaks for 4-2 in the third.

Nishikori quickly goes up 30-0 then leaves a space to invite a sweeping single-handed Wawrinka crouched backhand for 30-15. Wawrinka levels at 30-30, Nishikori hits back but a backhand down the line brings up the deuce.

Wawrinka blinks first on a baseline rally to give Nishikori advantage and he hammers a forehand winner on the next point to take the game.

Another tight game goes Nishikori's way

Wawrinka, still wearing his Manchester City-esque light blue, holds his serve and it is 1-1 in sets and 1-1 in games.

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A change of colours for Nishikori in between sets. He changes from a red shirt to a white one, and immediately holds his serve in his new outfit.

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John Morris, who represents Nick Kyrgios, says: "Nishikori needed a good start to the second set and if he had gone down a break then I think it would've all been over. But he has just shown what a warrior he is and what a fighter he is."

Nishikori has a set point. Wawrinka slams his first serve in the net, and then double faults. What a way to win the set. One set each.

Image source, AP

Some interesting reaction coming from Victoria Azarenka's camp following her straight sets defeat by Ekaterina Makarova earlier today in the women's singles quarter-finals.

Image source, Reuters

In the immediate aftermath of the tie, Azarenka's spokesman told reporters that the player had suffered food poisoning and had been vomiting in the run-up to the quarter-final, but the Belarusian would not comment further.

"I don't really want to talk about it," Azarenka said. "I just want to give credit to my opponent. She played really well today. "Yes, I'm disappointed, but I feel like I tried my best with whatever I had. I just want to wish her good luck. That's it. I'm out of the tournament."

Ben believes this set is crucial to Nishikori's changes of winning. Well, it is now 6-5 to the Japanese player. We may well be heading to a tie-break.

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American journalist Ben Rothenberg: "If Wawrinka gets a 2-0 sets lead then Nishikori will be out of it."

It is now 5-5. Wawrinka leads by one set, with it going on serve in the second.

Despite wasting a glorious opportunity to break Wawrinka in the previous game, Nishikori maintains his confidence to hold his serve and go 5-4 ahead in the second set.

Image source, Roger Federer

Second seed Roger Federer on Twitter:, external Playing my US Open quarter-final match tomorrow at 8pm EST (01:00 Friday, BST) in that beauty over there #ArthurAshe.

Federer is in the bottom half of the draw and meets France's Gael Monfils in his quarter-final.

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John Morris, who represents Nick Kyrgios: "People ask if Nishikori can win a Grand Slam? But it is things like that, where he had three break points, which makes me think that he can't. He just does not have the weapons over seven matches."

He had to fight hard to win the last game, and Nishikori has a chance to break Wawrinka. The Japanese player, the 10th seed in the competition, has the score at 0-40 and has three break points, which he then wastes.

Image source, Reuters

A huge missed opportunity. An ace for Wawrinka seals the game and a let off for the Swiss.

Good spirit shown from Nishikori as he saves two break points in the seventh game. Remember, he lost the opening set 6-3 and the second set is still going with serve. Just about.

Image source, Getty Images

Easy one this for Wawrinka. Holds his service game to love. On to the next game.