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NOW: Alexander Zverev beats Carlos Alcaraz 6-1 6-3 6-7 (2-7) 6-4 in men's quarter-finals
German will play Daniil Medvedev, who beat Hubert Hurkacz 7-6 (7-6) 2-6 6-3 5-7 6-4
Qualifier Dayana Yastremska beats Linda Noskova in straight sets to reach first major semi-final
Zheng Qinwen beats Anna Kalinskaya 6-7 (4-7) 6-3 6-1 to reach women's singles semi-finals
Britain's Neal Skupski and American partner Desirae Krawczyk reach mixed doubles final
Zverev 6-1 6-3 6-7 (2-7) 2-2 Alcaraz*
Alexander Zverev was two sets up before losing to Dominic Thiem in a memorable 2020 US Open final, but can Zverev get the job done tonight?
A hold to 15 and the sensational serving which has been there throughout most of the match before the tie-break makes a much-needed return.
*Zverev 6-1 6-3 6-7 (2-7) 1-2 Alcaraz
Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds
Carlos Alcaraz is going out after Alexander Zverev's second serve and he's tried to do that throughout this match from the beginning. He hasn't had a lot of success but it's just starting to build.
*Zverev 6-1 6-3 6-7 (2-7) 1-2 Alcaraz
A hold to 15 for Alcaraz, who is fired up and firing. The momentum is swinging back in his favour.
Zverev 6-1 6-3 6-7 (2-7) 1-1 Alcaraz*
Image source, Getty Images
Image source, Getty Images
Image source, Getty ImagesZverev 6-1 6-3 6-7 (2-7) 1-1 Alcaraz*
It is not far short of 1am local time, but there's still a large crowd there loving what they are witnessing.
Another sensational rally, this time 22 shots, goes Alcaraz's way, 30-0.
Zverev 6-1 6-3 6-7 (2-7) 1-1 Alcaraz*
Zverev's fourth-set advantage lasts a couple of minutes before Alcaraz instantly gets the break to put us back on level terms.
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What a sport tennis is! Potentially two mins from end switches to maybe another two hours. Bring it on!
Rickey, Essex
*Zverev 6-1 6-3 6-7 (2-7) 1-0 Alcaraz
Can Alcaraz instantly bring us back level? He has two break point chances to do so, 15-40.
Zverev 6-1 6-3 6-7 (2-7) 1-0 Alcaraz*
No mental drop-off from Zverev after losing that tie-break having come so close to sealing the victory.
Zverev gets the break of serve immediately at the start of the fourth set to again put himself in pole position.
Zverev 6-1 6-3 6-7 (2-7) 0-0 Alcaraz*
Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds
Zverev has been so good at the net this evening - but I felt like Alcaraz let him escape one there. That may have been youth shining through. That should have been Alcaraz's point.
Zverev 6-1 6-3 6-7 (2-7) 0-0 Alcaraz*
Zverev quickly earns two break points in the opening game of the fourth set. Great sprinting from deep from him to get there, the pair trade volleys at the net, with it going Zverev's way.
Zverev 6-1 6-3 6-7 (2-7) 0-0 Alcaraz
Jonathan Jurejko
BBC Sport in Melbourne
While Alexander Zverev receives treatment on his foot, Carlos Alcaraz sprints to the baseline to keep warm.
He jogs over to where his team is sitting, grabs another bottle of fluid which is dropped down and smiles as they chat.
Meanwhile, the extended break allows the fans who haven't moved from their seats for over two hours - unless they were jumping up in celebration - to go inside for a comfort break.
Zverev 6-1 6-3 6-7 (2-7) 0-0 Alcaraz
We've got a medical timeout at the moment as Zverev, who took a heavy fall during that third-set tie-break, gets some plasters and tape stuck on to his toes.
Zverev 6-1 6-3 6-7 (2-7) 0-0 Alcaraz
Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds
We saw maybe one or two points where Zverev got a little tight - and boy, he was made to pay a heavy price. It's still a long road for Alcaraz to come back, though.
Zverev 6-1 6-3 6-7 (2-7) 0-0 Alcaraz
Russell Fuller
Tennis correspondent on BBC Radio 5 Sports Extra and BBC Sounds
That was spectacular. Everything looked beautifully combined from Carlos Alcaraz.
Zverev 6-1 6-3 6-7 (2-7) Alcaraz
Jonathan Jurejko
BBC Sport in Melbourne
Wow! Carlos Alcaraz simply ripped the ball in that tie-break.
The whole stadium is stunned - but nobody more than Alexander Zverev.
Alcaraz is back in business and he looks completely chill.
The grin has returned, as has the spring in his step.
Game on!
Zverev 6-1 6-3 6-7 (2-7) Alcaraz
Mark Woodforde
17-time Grand Slam doubles champion on BBC Radio 5 Sports Extra and BBC Sounds
We've been speaking so highly of when Alexander Zverev has been getting into net tonight. It's just changing now. He hasn't had the same success when going forward in the last 15 minutes.
Zverev 6-1 6-3 6-7 (2-7) Alcaraz
Alexander Zverev was two points away from victory on his own serve, but he has just been blown away in a stunning tie-break performance from Carlos Alcaraz, winning six points in a row with some delightful, perfect passing shots.
Into the fourth we go. And this has the makings of turning into a classic.
Four set points for Alcaraz and what a forehand down the line to get to that point, 6-2.
Alcaraz sends Zverev dashing with a forehand wide and then unleashes the forehand winner, 5-2 Alcaraz, two points away from taking this into a fourth set.