Nadal comes out on top after a thrilling rally, which finishes in a net battle.

With the advantage in his back pocket, Dolgopolov flies a return over the whitewash and Nadal holds.

Nadal switches to the shady side of the court. Shady as in lacking sun, not as in devious.

The Spaniard pummels a huge serve past his opponent for 40-0, but the hold to love escapes him when Dolgopolov finds a sensational backhand reply on the next point.

Then a double fault from Nadal makes it 40-30, before deuce. A good comeback from Dolgopolov, this.

Image source, Getty Images

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Piers Newbery
BBC Sport at Flushing Meadows

"As a courtesy to the players, please keep noise to a minimum," says the announcer. At least I think that's what he said.

The constant chatter from 20,000-plus spectators is actually not too bad from sitting in the stands, like a continual low hum in the background that you quickly get used to. It might be a bit trickier when you're playing tennis and trying to hear the ball on your racquet though. "It's a bit much, no?" Nadal said after his first match.

Dolgopolov's rather unorthodox serve is causing him some issues at the moment.

Another double fault hands an early break point to his opponent.

The unseeded Dolgopolov comes streaming into the net and tries to swing a forehand on to the baseline, but it clears it.

Nadal takes the break.

David Law
Radio 5 live sports extra commentator at Flushing Meadows

That's an example that Nadal has got his eye in early. He saw those shots coming at him, and they were coming at him quickly.

The perfect start for the world number one.

Nadal overpowers his opponent with a massive serve for 30-0.

He watches Dolgopolov shoot long after a decent rally to make it 40-0, and then the Ukrainian nets.

Image source, EPA

A woeful start by the Ukranian. A double fault!

But Dolgopolov makes up for it with a sensational double-handed backhand winner into the corner.

He holds when Nadal spanks a backhand way over the baseline. Not a clean hold, but a hold none the less.

*denotes next server

Image source, Reuters

David Law
Radio 5 live sports extra commentator at Flushing Meadows

Dolgopolov is one of my favourites to watch. On his day, if he's zoned in and ready and not whinging and finding an excuse, he's a fabulous shot maker. We could be in for some furious exchanges here.

This is the first time this pair have met in a best-of-five match.

Reckon it will go all the way today? Let's see...

Dolgopolov will get us under way on Arthur Ashe Stadium.

This is the 28-year-old Alexandr Dolgopolov's best run at a Grand Slam since he reached the quarter-finals of the Australian Open in 2011.

He cruised into the fourth round in New York with a speedy win over Serbia's Viktor Troicki, winning 6-1 6-0 6-4. He hit 24 winners and came through in one hour and 21 minutes.

But the result was somewhat overshadowed by matters away from the US Open, when it was revealed Dolgopolov was being investigated by the Tennis Integrity Unit following his defeat by Thiago Monteiro at the Winston-Salem Open.

The Ukranian insisted the investigation wasn't on his mind, though.

"If people want to write something, they write something. You can't stop them from doing it. It's just not under my control," he said.

Image source, Getty Images

Top seed Rafa Nadal is bidding for his seventh US Open quarter-final appearance and his first since winning the title in 2013.

He's also looking for his 50th victory at Flushing Meadows.

The Spaniard hasn't had the simplest run so far. He got past Dusan Lajovic without much drama, but needed four sets to beat Taro Daniel of Japan and Leonardo Mayer from Argentina.

Nadal has a 6-2 head-to-head lead over today's opponent, Alexandr Dolgopolov.

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Piers Newbery
BBC Sport at Flushing Meadows

Sympathetic applause around Ashe as Brady's challenge is swatted aside in 46 minutes, just as the bulk of day session spectators are making their way up the escalators and into the giant stadium, most balancing trays from the food court. It's gone 12pm, it's officially lunch time.

Nadal should enjoy the warmer conditions as they might draw a little pace from a court that is generally thought to be on the slow side.

What time is it?

It's vamos time.

Image source, Getty Images

Karolina Pliskova after her 6-1 6-0 victory over Jennifer Brady: "I really wanted to get the chance I got from the last match. I wanted to play a little bit better and today I was much better. I think she was a little bit nervous, first time on Ashe, and that's normal, so I wanted to take advantage from that. Hopefully I'll be here for the next match as well. "

That's a terrible shot from Jennfier Brady I'm afraid, a forehand volley that ends up thudding rather mournfully into the net. That's match point to Pliskova...

Image source, Reuters

A little bobble off the net goes against Pliskova to put Brady 30-0 up, but a double fault from the American gets her opponent on the board.

Ooh, a forehand error from Brady cuts her lead, before a backhand winner from Pliskvoa takes us to deuce.

Back to back aces from Pliskova fire her ahead before Brady draws the error out of the Czech's backhand.

The American drops too short with her next shot, though, and it's so easy for Pliskova to dart in and carve a winner, before a loopy backhand from Brady goes out.

Just one more game for Pliskova to reach the quarter-finals...