Eight unforced errors for Sabalenka in that first set compared to Pegula's three.

Back under way for set two and it's the Belarusian to serve first.

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra and BBC Sounds

I think Sabalenka just needs to settle down, she looks like a rabbit in headlights.

Image source, Getty Images

Sabalenka made a swift exit from Arthur Ashe after that opening set. Not surprising. Things were starting to go really wrong and frustrations were bubbling over.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Now we're seeing more of Sabalenka's demonstrative side.

The top seed jabs her temple as she stares down her team, then rotates her neck in attempt to relieve some stress.

Then it's hands on hips as Pegula fires another forehand winner away for set point.

Pegula's steely clenched fist indicates how locked in she is. Impressive fightback.

Well we just said Pegula has not taken a set off Sabalenka for two years...What a time to do it.

The Belarusian's passing shot down the line drops wide and Arthur Ashe loves to see it.

Pegula brings up three set points as she sends Sabalenka one way then the other then wrongfoots her with a forehand to the corner.

Sabalenka points to her head as she looks up at her coaching box when a return drops wide.

The frustration is really starting to show here as she again misses the shot at the net for 30-0.

Pegula is one service game away from taking this first set.

She hasn't taken a set off world number one Sabalenka for two years.

Image source, Getty Images

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra and BBC Sounds

This is inspired tennis from Pegula. She is getting onto the ball quicker, doing more damage with the shots she is hitting and making every volley virtually impossible to return.

Goodness me. Now the crowd are on their feet.

The momentum is all on Pegula's side of the court as she somehow keeps the ball in play and draws another error from Sabalenka.

The Belarusian is fuming as she heads back to her chair and puts her towel over her head.

A huge roar from Sabalenka as her backhand down the line gets her to 15-15 on serve but all of a sudden Pegula has a break point.

Sabalenka drives into the net but the American sends a passing shot zipping past her.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Now Ashe has woken up.

Pegula breaking back and levelling has raised the volume.

Maybe the Honey Deuce has started kicking in, too.

That's a great passing shot from Pegula and it has sections of the crowd on their feet at 30-0.

Another mistake from Sabalenka puts us firmly back on serve.

Annabel Croft
Former British number one on BBC Radio 5 Sports Extra and BBC Sounds

That was a terrible game from Sabalenka. It was won purely from errors, it wasn't a great game from Pegula.

Image source, Getty Images

Pegula goes long and that wipes out one break point but it's a double fault from Sabalenka which ultimately hands the American the break back and the crowd are well behind their player now.

Hello...

A couple of errors from Sabalenka and Pegula has two break-back points. We said dealing with frustration would be key for Sabalenka, let's see what she's got.

David Law
Commentator on BBC Radio 5 Sports Extra

Pegula is playing a good match so far, but she is 4-2 down.

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

Aryna Sabalenka has learned how to quell the New York crowd in the past couple of years.

In the 2023 final against Coco Gauff, the ferocity of the atmosphere got on top of her as Ashe willed the American teenager to victory.

Sabalenka learned to block out the noise when she beat Emma Navarro and Jessica Pegula on her way to the title last year.

But, with all due respect to Navarro and Pegula, they don't stir the emotions of Flushing Meadows like Gauff does.

Pretty tame atmosphere - even under the roof.

There it is. Another forehand pummelled across court gives Sabalenka the crucial break she was probing for.

Pegula rallies to get to deuce then a long Sabalenka return of serve hands her game point.

But again Sabalenka is on the attack and works herself another break point opportunity with a crunching forehand into the corner.