BBC Radio 5 live sports extra

Zverev had a break point in that mammoth game and put so, so much effort into it. But it all counts for nothing eventually as Nadal survives the scare to move 4-1 ahead.

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The capacity crowd in at the Rod Lever Arena are certainly getting their money's worth. We have just seen a 27-shot rally, the longest of the match.

A number of two-handed backhand returns from Zverev seem to be hit harder and harder each time but Nadal is equal to every question, before Zverev can only hit the top of the net. Great stuff.

But we are not done just yet and Zverev takes us back to deuce shortly after. You get the feeling this is a crucial game for both players.

Loud grunts from Rafael Nadal as he storms to the net after serving deep before he punches away a volley.

A Zverev forehand is then challenged by Nadal, but it is a bad decision from the former world number one as the ball clearly hit the baseline.

An ace from Nadal makes it 30-30. Will the German be able to break serve? He screams 'come on' after a wonderful passing backhand gives him a break point, but Nadal comes up with a special serve when he needs it and we go to deuce.

Zverev leads two sets to one but a weak return hits the bottom of the net at the start of the fourth game of set four, but the German takes the next two points, including an ace, to lead 30-15.

Zverev thinks a Nadal return has gone long and stops in his shot, but his judgement is a bit off and reacts too slowly, looping the ball into the air, well short of the net.

But it does not matter, he later holds his serve, a much-needed confidence building hold and Zverev is on the board in the fourth set.

Now this is a test of character for the 19-year-old. Rafael Nadal is a man on a mission. He moves 40-0 up, but a serve to Zverev's backhand is well returned and the Spaniard goes long.

But it is only a brief respite as Zverev overcooks a return and Nadal, in next to no time, is 3-0 up in this set with a tight stranglehold on this set.

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June Campbell: WOW what a match this is turning out to be. Both players fighting for every point. Incredible.

More fist-pumping from Nadal, a sliced backhand opens up the opportunity, he dashes into the net and an overhead smash gives him his fourth break point.

This time he takes it. Get yourself comfortable, this could well be going all the way.

An early chance for Rafael Nadal for a quick break of serve as he edges out a monster, gruelling rally to take the opening two points off the Zverev serve.

Nadal then moves to break point and the teenager serves into the net, but the second serve is deep, forcing Nadal to go wide with a forehand.

A crushing forehand from the German saves the second break point, before an ace takes us to deuce. This will be some hold of serve from 0-40 down.

Theo Bowyer: Mark my words Zverev will win a major one day... his backhand is dynamite!

An ideal start to the fourth set for the ninth seed Nadal as he serves out the opening game to love.

Well, this is not in the script. Rafael Nadal, a winner in Melbourne in 2009, is in trouble in the third round against 19-year-old German Alexander Zverev.

Zverev took the opening set 6-4, lost the second 6-3 but quickly recovered to take the third, via a tie-break. How will Nadal respond now? Don't go anywhere.

Leon Smith
Great Britain Davis Cup captain on Radio 5 live sports extra

Zverev played the more aggressive in the tie-break, he was on the front foot and it has paid off. What a great reaction from Zverev at the end of the set and I have to say I think he deserved it.

He responded well after losing the second set, had some vital holds early on and started to serve very well. 

Zverev goes for the big serve but hits the net. There's a murmur of disappointment from the crowd.

And he's done it! And what a shot to do it with! A superb backhand, smashed from out wide and Nadal can't get the racquet to it. Lovely, lovely stuff. 

"Come on!" shouts Nadal as he risks a flat serve, and a whip forehand gets him the point.

And now it's Zverev that's shouting, pumping his fists to the crowd, as Nadal overworks a forehand. Set point!

Leon Smith
Great Britain Davis Cup captain on Radio 5 live sports extra

It is great tennis. We are seeing some really good points.

Zverev's at the net again, meeting a low delivery, but it's too low for that cute little dink and he hits the net.

His response? Up to the net again, a rally going on right at the net, but this time a smash beats Nadal.

Nadal crashes his serve in and his responses are deliberately short, trying to get Zverev to the net. Zverev obliges - and whack, there's the forehand, sending Nadal the wrong way.

Nadal takes an age for his next serve, getting yells of encouragement as he steels himself. It doesn't work though as Zverev batters a backhand past him.

Zverev struggles with his second serve, missing Nadal's response and hitting the forehand wide.

A grunt of agitation from the 19-year-old and he has Nadal running all over the place, but he misses again! He came up to the net, put too much on the shot and out the ball went.

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