Here we go.

Nava comes forwards and slams a forehand into open court for 30-30, but goes long on the next one and that's break point.

Will these rallies never end?

The next one is 27 shots long, with the 27th going into the net off Murray's racquet to make it 15-30.

OK. Calm down. Andy Murray has won the first two points as Emilio Nava serves for the set. 0-30.

Jonathan Jurejko
BBC Sport at Flushing Meadows

Fair to say Emilio Nava wears his heart on his sleeve. Great to see - unless you're Andy Murray.

The youngster roars after beating Murray with a brilliant backhand winner to set up break point, turning to his box with a passionate celebration.

That is followed by another when he takes the break with an overhead and then implores the crowd to give him more noise.

Naomi Broady
British player on BBC Radio 5 Live

This has been so physical - they had only played seven games in just under an hour, with an average rally length of over five shots.

It is obvious how much Nava is enjoying it because of how loose and free he is playing, not to mention smiling up at his box.

There is a huge gulf in energy between the players now. Andy is looking pretty dejected.

It's a lengthy rally. Nava comes forwards, Murray goes for the lob and... Nava smashes it back out of Murray's reach.

Timed to perfection. Nava will now serve for the set. He wafts his arms around trying to get more noise out of the home crowd.

Oh dear, Murray shrugs his shoulders after a double fault puts him back to deuce.

Nava sprints left on the next point and hits a backhand winner hotter than the New York sun to set up another break point.

Murray's coach Ivan Lendl looks as nonplussed as ever in the stands. He's gone for a wide-brimmed hat today, very sensible in this sun.

Phew. Nava goes long.

Murray will need all that knowledge, because he faces break point.

Jonathan Jurejko
BBC Sport at Flushing Meadows

When Andy Murray was asked on Monday what he knew about Emilio Nava, most probably expected the answer to be not a lot.

But as we know Murray is a student of the game, and it turned out he knew the 20-year-old better than many might have thought.

"I actually hit with him a couple days ago, so it was good to get on the court with him," he said.

"Otherwise, I saw a little bit of his match but actually being on the court with someone and feeling their shots is helpful when you don't know loads about them."

Murray gives Nava a look at a second serve, but the former world number one intimidatingly sprints forwards to the net and the American can't land his lob.

Murray misjudges a drop shot next and that's deuce.

Emilio Nava's first-round victory was his first win at tour level.

But he looks pretty comfortable faced with former Grand Slam champion Andy Murray's serve.

He sends Murray running all over the place, then sends down a smash for 30-30.

David Law
Commentator on BBC Radio 5 Live

The flip side is Murray hasn't broken yet and his frustration might rise, and at the same time Nava's confidence will rise.

Murray might go to his chair for this changeover a little miffed.

Image source, Getty Images

Jonathan Jurejko
BBC Sport at Flushing Meadows

Another pause by the server as a fan casually wanders down to a front row seat mid-game.

Nava turns and gives her a sharp look, with another spectator ushering her to sit down quickly with his hands.

Some people...

The French would have been booing, whistling and slow-clapping her by now at Roland Garros.

It initially looked like that game wasn't going to be any easier for Nava. He hits what looks like a backhand winner into the corner but somehow Murray gets a racquet on it and the American has to hit another huge forehand just for 15-0.

At 30-15 down, Murray again expresses annoyance at fans coming in in his eyeline and he doesn't do much else from there.

Nava gets a hold and it didn't take him 13 minutes. What a treat.

Naomi Broady
British player on BBC Radio 5 Live

Nava's last service game was about 13 minutes long. Andy Murray just got that game in just over a minute.

Bit harsh, really. After making Emilio Nava work so hard for that game, Murray holds to love in a matter of minutes.

Over to you, Emilio.

Jonathan Jurejko
BBC Sport at Flushing Meadows

This seems to be a case of who is going to tire - mentally or physically - first.

Early evidence would suggest Nava's serve can't continue to withstand this pressure and Murray will sure as heck want to keep piling it on.

Nava's first service game took 14 points for him to get over the line before being topped by that marathon game.

Lasting 20 points, Nava had to stave off two break points and seven deuce before holding.

It's over! (The game, not the match)

Emilio Nava finally gets his hold.