Image source, Reuters

Aryna Sabalenka breaks early in set two.

She was under pressure at 0-30 in the opening game but the Belarusian has a look of steely determination now and another big ace helps her fight back to hold.

A fabulous forehand winner comes before she sprints in to reach an Amanda Anisimova drop shot and sneak it past the American to go up 15-30.

The top seed earns the break point and takes it as Anisimova's forehand goes long. The 16th seed is frustrated and throws her racquet onto the court - and is duly given a warning by the umpire.

Ben Shelton deals with an awkward bounce off the net well to get to 30-30 and save himself from having to defend two break points.

The American takes a deep breath as Carlos Alcaraz goes into net, before serving a huge ace to hold.

Not even four-time Grand Slam champion Alcaraz can do anything about that.

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

He is taking his time Carlos Alcaraz. Going for broke, no fear, once again.

He is so quick, by far the quickest along with Gael Monfils in his time.

Carlos Alcaraz plants a couple of loose forehands into the net to give Ben Shelton half a chance at 30-30.

He kicks some loose clay away before serving, and comes out on top of a rally.

Alcaraz seals the game with a big first serve, followed by a "vamos!"

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

I really admire how Aryna Sabalenka's going about her business on court. She's utterly fearless.

Image source, Getty Images

It's taken a little longer than it seemed it might but Aryna Sabalenka takes the first set.

The world number one looked in control early on but once Amanda Anisimova was put under real pressure, she responded and we got the slug-fest that was anticipated.

Sabalenka was briefly knocked off her stride but having secured that crucial hold, she attacks the Anisimova serve and breaks again to avoid the tie-break.

Ben Shelton eases into a 40-0 lead as Carlos Alcaraz plants into the net from the back of the court.

The American then wins an exchange at the net to hold to love.

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

Stunning.

You can feel and see the ball hold on the strings for such a long time when Carlos Alcaraz plays it.

It's amazing to witness.

Carlos Alcaraz comes through his service game relatively untroubled, finishing it off with a delightful drop shot which Ben Shelton can do nothing about.

Image source, Getty Images

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

It was a stumble and I don't know what happened. I don't know if Carlos Alcaraz's foot got caught in the clay.

Going down can get into your head. Alcaraz is acting a bit more gingerly with how he's moving around the court.

Two tricky serves from Shelton with a load of top spin has Alcaraz scrambling and the second seed is made to look a bit foolish as he returns them both with looping wide shots.

Still nothing to split them.

Image source, Getty Images

This was billed as a big test for Aryna Sabalenka and if that didn't seem to be the case for much of the first set, it does now!

Amanda Anisimova had her back against the wall and has come out fighting, breaking back, holding with relative ease and now earning two more break points with some brilliantly crisp hitting.

Sabalenka is the one having to dig in now and she lets out a huge roar as she saves the second of the break points.

A big ace secures the hold for a slightly relieved Sabalenka. Anisimova will now serve to force a tie-break.

Top response from Shelton who wellies a forehand down the line which Alcaraz can't get a clean racquet to.

Here we go, we have our first opening as Ben Shelton loses a battle at the net, volleying into the top of the net cord.

30-40.

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

Ben Shelton is a dangerous player and he is capable of causing problems.

But can he maintain this throughout the match?

Image source, Getty Images

No panic. Carlos Alcaraz hits a delicious drop-shot winner to set up game point and then forces an error out of the American.

But here comes Shelton. At 40-15 he hits a 98 mph forehand winner down the line, and then backs it up with a passing backhand, cross-court stunner.

Deuce.

Superb from Amanda Anisimova.

With Aryna Sabalenka serving for the set, the American knows she has to attack - and does so brilliantly.

Sabalenka saves one break point and then spurns a set point before Anisimova earns another break chance.

No mistake from the 16th seed this time, some crunching ground strokes and eventually there is a forehand that Sabalenka can't get back. Back on serve in the first.

But here comes Shelton. At 40-15 he hits a 98 mph forehand winner down the line, and then backs it up with a passing backhand, cross-court winner.

Deuce.

Image source, Getty Images

He might have some swagger, but Carlos Alcaraz has a demon first serve. He races to 40-0.