Pegula takes Barty to 30-30 but miscues with a forehand chance. The Australian gives her opponent another chance though with a double fault. Deuce.

Ash Barty rips down an ace but can only skip a backhand slice after a baseline exchange off the next point. Another ace follows, naturally... 30-15.

Jessica Pegula looks a little like she's revealed a puzzling series of letters during a morning Wordle session. Facing Ash Barty will do that to you.

But, almost like taking a long swig of coffee, the American finds focus and manages to unpick this particular puzzle to edge to 40-30 and then hold. She's on the board.

Pegula tries to leap all over a second serve but prods wide and Barty rattles down an ace to hold and consolidate that opening break.

A succession of corking serves from the world number one before Jessica Pegula fires in a punchy return. 30-15.

And this time Ash Barty gets the break!

The top seed just cranked through the gears after slipping 40-0 behind. Ominous.

Brilliant from Ash Barty. Her return forces Jessica Pegula wide and the Australian saunters in to whip away a short ball and bring up another break point.

An undercooked slice from the world number one and that's deuce for the second time.

Wonderful forehand from Ash Barty, leaning back on the baseline but lashing it into the corner.

Break point Barty.

Deuce! Ash Barty took a few points to warm up, but from 40-0 has won three points in a row to put some pressure on Jessica Pegula.

Ash Barty gets on the board at 40-15 with a dipping backhand that Jessica Pegula can't lift over the net from close range. That gets a cheer from the Melbourne faithful, and a careering dart forward from the Aussie that forces her opponent long gets an even bigger one. 40-30.

A little hop behind the baseline from Ash Barty as a return drifts long. The next is on the money, but Jessica Pegula reads the exchange well and pops off a forehand winner.

30-0.

Right then, away we go.

Jessica Pegula will serve first.

Ash Barty was the victor in her only previous meeting with Jessica Pegula.

Barty's 6-3 6-3 victory over Pegula came in the first round of the French Open back in 2019, where Barty would go on to claim her first Slam title.

The players have arrived on Rod Laver Arena. The fans are still sauntering in after refuelling.

Jessica Pegula is into the Australian Open quarter-finals for a second year in a row.

She registered an excellent 7-6 (7-0) 6-3 victory over fifth seed Maria Sakkari in the fourth round to set up the meeting with Barty.

She has only dropped just one set at Melbourne Park and that came in her opening match again Anhelina Kalinina.

Pegula has said she has been relaxing by spending her evenings in the casino where she is staying, saying playing blackjack "got me kind of thinking about strategy, but at the same time, it would kill some time and relax me."

Image source, Getty Images

World number one Ash Barty has yet to drop a set at this year's Australian Open.

Her astonishing streak of 63 consecutive holds of serves was broken by Amanda Anisimova in the fourth round, but Barty shrugged that off to beat the talented American 6-4 6-3.

Barty's best performance in her home slam came in 2020, when she reached the semi-finals before losing to eventual champion Sofia Kenin.

She came unstuck at the quarter-final stage last year, where she fell in three to Karolina Muchova.

Image source, Getty Images

Still to come...

World number one and home favourite Ash Barty is up next on Rod Laver Arena.

And here is Rafael Nadal: "I don't know, honestly I was completely destroyed! A very tough day, very warm, I didn't practice for it. I was a little bit lucky at the beginning of the fifth. At the beginning of the match I was playing great, I know how difficult it is to play against a player like Denis.

"I had my chances at the beginning of the third, I didn't get it and then started to feel a bit more tired and he pushed me. For me it is amazing to be in the semi-finals.

"I started to feel not very well in my stomach so I asked for something, they took the tension, checked everything was all right in my body and some tablets to try and improve my stomach - so-so, I think I was lucky I was serving great in the fifth.

"I am not 21 anymore, after this match it is great to have two days off. I felt quite good physically in terms of movement but the conditions haven't been that hot.

"For me it is everything to be able to play one more time in that semi-finals match.

"We can create history but the real truth is two months ago we didn't know if we would be back on tour at all, so it is just a present of life I am here playing tennis again and enjoying it."

In a very relatable moment, Nadal tells the crowd that "he's not 21 any more."