Russell Fuller
BBC tennis correspondent

Serena Williams looks unencumbered by any of the pressure of chasing her 24th Grand Slam title. She is playing so well...

Image source, Getty Images

This is a serious level from Williams. She's knocking the spots off the ball.

Exhibit A as she rocks Azarenka with a deep forehand into the corner on the deuce side, following it up with another.

Wham, bam, goodnight ma'am. That's 30-15 and Serena heading towards another comfortable hold...

Azarenka was so annoyed with her 41% first serve percentage, she described it like most of us would. Clue: two of the three words were expletives.

Phew! Azarenka sighs relief as she finally lays a glove on Williams. Still she struggles to land her first serves regularly, but does enough to get on the board.

A snarly look is flashed across to her box, though, as she swipes her towel from the chair at the changeover.

Not a time for meditation, yet.

Crunch! Bang! Pow! Twhack!

This is like an episode of old-school Batman. And it is Williams who is laying down the law like Adam West.

Intense hitting from the six-time champion, who batters her way to another comfortable hold.

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David Law
BBC Radio 5 Live Sports Extra tennis commentator

This is way better tennis than we have seen from Serena Williams all tournament long. It is like she is taking it personally that some people have tipped Victoria Azarenka to win.

Vika sticks out her bottom lip and almost shrugs at her box. Too good from Serena.

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One break is bad news. Two would be catastrophic.

More worries for Azarenka at 15-30, only to respond with a hammer of a forehand winner. Nerves eased? Hmmm, not quite.

Williams slugs back with some heavy hitting of her own, landing another blow with a forehand crosscourt winner.

Break point... and Williams takes it when Azarenka laces a forehand from well behind the baseline wide.

David Law
BBC Radio 5 Live Sports Extra tennis commentator

I think that Serena Williams will win because she remains the greatest player of all time and I think that the fire still remains in her belly, even if the form lines suggest Victoria Azarenka is more likely.

After about 90 seconds, Vika has lost as many games as she did in the entirety of her quarter-final match...

And a couple of minutes later, that tally has been doubled.

Williams hits a howitzer of a cross-court forehand winner, sandwiched in-between two double faults herself, before seeing out the hold.

Nerves on both sides of the net, then.

Russell Fuller
BBC tennis correspondent

That is the worse possible start for Victoria Azarenka and, no matter what experiences and tournaments you have won, that must be unsettling.

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Uh oh... Azarenka in trouble around. A double fault for 15-30 doesn't help, Williams pouncing on a couple of second serves to earn two break points.

Jingle jangle... the nerves are clear. Azarenka overcooks the second serve and it is another double fault.

Worst. Possible. Start.

Vika to seek-a hold in game one. Ready? Play.

Serena is back on court, obvs.

Where has Victoria Azarenka's form come from? Sensational stuff.

Most had written the Belarusian off as a force. Not surprising as she barely won a match in the 18 months going into the Cincy-US Open bubble.

Then it all turned to gold for the 31-year-old.

She has won 11 matches on the bounce, helping her win the Western and Southern Open, and showing glimpses of the form that led her to two Australian Open titles and the world number one spot in the early 2010s.

Presume we're all in agreement that those pre-match interviews are useless. Cagey to say the least.

So I don't feel too bad that I didn't get the quotes down.

Serena has disappeared behind the scenes, not sure why. Azarenka lurks on the baseline while she waits.

Hello! You're not thinking of sneaking off to sleep, are you? Better not be.

You'd be a fool to even consider it. Your boss will understand in the morning, I'm sure.

Serena Williams in the one corner, Victoria Azarenka in the other. Both are aiming for Rocky-style fairytale comebacks...

Has the kettle brewed yet? Barely, I'd imagine.

No messing about on Ashe as Osaka and Brady are swapped for Williams and Azarenka quicker than a substitution at Wembley.

Right, we will be back shortly with the mother (geddit?) of all US Open semi-final clashes as Serena Williams takes on Victoria Azarenka.

Jonathan Jurejko will be tinklng the keys for that one.

Bye for now.

Number four seed Naomi Osaka: "I consider New York a second home, this courts suits me well. I felt like I was sticking it out. Jennifer Brady gave me flashbacks to playing Kvitova in Australia.

On her possible final opponent: "I don't know. They are both so good."

Jennifer Brady departs, mask in place. She has been immense.