A furious swipe of the racquet from Mayer as, from 0-15 up, he sees himself 40-15 down through a forehand that goes sailing out of play.

Nadal's first serve isn't bang on and a double fault hands Mayer another easy point. Mayer keeps himself in the rally, Nadal running up and down, but the Spaniard cracks a forehand winner cross-court to hold.

Leon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows

Mayer's serve is really good. He mixes it up well and has the power. He's already saved six break points and his serve gets him out of trouble.

Image source, Getty Images

An ace down the T, at 126mph, saves the first, and then a Mayer volley, on the move, tidies up the game. Excellent work.

* denotes next server

The first break point is saved as Mayer takes a step in and slices a backhand over and Nadal, hurried, pushes his forehand into the net.

Nadal then challenges the call as his backhand is called long - and the umpire was right. Out by a mile. Deuce.

Nadal feints a move left and then spins a forehand winner to the right of Mayer, before a rally goes the Spaniard's way as Mayer's backhand lets him down.

Mayer keeps pushing him though, sending down backhand after backhand, and eventually it's Nadal who shanks the ball into the crowd.

Another forehand error from Mayer, though, and Nadal has two break points once again.

A big serve out wide from Nadal to get this game going.

Ooft, that's superb work from Mayer though, chasing down a bit of Rafa drop shot trickery and volleying a backhand short of an advancing Nadal. The Spaniard responds with an almighty forehand of his own, though, and Mayer can only tonk it wide.

Image source, Getty Images

Piers Newbery
BBC Sport at Flushing Meadows

Weather update - there's a storm brewing, and no mistake. Cold, breezy and spots of rain in the air, demanding Wimbledonesque hardiness from those spectators not lucky enough to be under the stadium roof.

Fashion update - Nadal's ferociously pink top, as seen on TV, is actually a much softer salmon hue in the flesh. Stay tuned.

Image source, BBC Sport

That's a better serve from Mayer. A bit more speed behind it catches Nadal off guard and he skews his return long.

Ace. Mayer holds.

Image source, EPA

Oop. Mayer, on deuce, serves up two double faults to hand Nadal another break point.

Can he make hay this time? Nope - he goes for the big forehand and ends up whacking the ball out of bounds.

Break point number four comes up in no time though, with a gorgeous forehand down the line... and then lashes another average forehand wide to take us back to deuce.

Leon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows

He's still trying to find that form. He's a fan of that whipped forehand and he's mistimed a few this evening. I know it's early in the match but that will frustrate Rafa.

Image source, Reuters

For the umpteenth time in this tournament, play is held up as a group of people come wandering in to find their seats. The food they've got looks good, mind.

Both players have a successful challenge before Mayer catches Nadal off-guard with a serve volley to get himself on the board.

Nadal pushes Mayer into the corner of the court and the responding backhand drifts out of play, handing the Spaniard two break points. Mayer saves the first with an ace before Nadal, looking to take on the second serve, carves a forehand long. Deuce.

World number one Karolina Pliskova hasn't been in the best form throughout this tournament, but she produced a brilliant comeback earlier on Arthur Ashe to beat China's Zhang Shuai.

Pliskova broke in the first game of the opening set but Zhang broke back and stunned the world number one to take the first set.

Zhang had the chance to serve out the match but stuttered, allowing Pliskova to win two consecutive games to force a final set.

In a tense decider, it was last year's finalist Pliskova that prevailed, letting out a huge roar as she moved into the fourth round.

Read the report here.

Image source, Reuters

Nadal goes through his endless pre-serve routine, which now includes a slight scratch of the head, before spinning a delightful forehand winner beyond Mayer.

It's all very sedate so far, Mayer furiously practicing his backhand slice in-between serves, and Nadal holds to 15.

Mayer, all in blue, flicks a fine backhand onto the tramlines to take a 30-0 lead, but his forehand goes long yet again to hand Nadal two points.

The Argentine fluffs slightly on his first serve but makes the next, and Rafa slaps a forehand out as Mayer holds.

Leon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows

You saw on Rafa's face when he walked on court, it looked more stressful than usual. Usually he's pumped up. There was definitely anxiety in his face. He's clearly feeling the nerves.

Nadal wasn't too happy with the noise inside Arthur Ashe when he played under the roof in the first round. He said it made it difficult to hear when the ball was hit.

He coughs up two double faults in this opening game but Mayer's forehand is a little wayward, and he overworks it twice as Nadal holds.

Leonardo Mayer has a special guest in his player's box today - his baby son, Valentino, who is quite happily perched on mum's knee.

It'll be Nadal to serve first.

So what of today's opponent?

Leonardo Mayer got his shot at the US Open after Milos Raonic withdrew from the tournament.

He's the first lucky loser to reach the third round at Flushing Meadows since Flavio Cipolla in 2008 - the last lucky loser to reach the fourth round of a Slam was Stephane Robert at the 2014 Australian Open.

Mayer has already dispatched with one name in this tournament - he beat 26th seed Richard Gasquet in four sets in the first round.

Image source, Getty Images

Nadal opened his US Open campaign under the roof of the Arthur Ashe Stadium against Serbia's Dusan Lajovic.

Lajovic served for the first set but Nadal broke back to love, won the tie-break and then barely looked back as he wrapped up a straight-set victory.

Taro Daniel proved a trickier ask in round two, as he took the first set and then went a break up in the second.

However, two fiery forehands from Nadal turned the second set around and he went on to register a 4-6 6-3 6-2 6-2.

Image source, Getty Images

BBC Radio 5 live sports extra

We've got live commentary available of Nadal v Mayer over on 5 live sports extra.

You can listen using the player at the top of the page, or by clicking here.