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Oh no, what's this? Carlos Alcaraz is crouching down and feeling his quad after missing a backhand.

Is it just cramp? Alexander Zverev thinks so and is demanding that they play on.

This could be trouble for Alcaraz.

Carlos Alcaraz produces a sublime backhand winner to get on the board at 15-30, and then reaches 30-40 when Alexander Zverev makes an inexplicable miss at the net.

The German shrugs it off with an ace to hold, however, and on we go in set three.

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Alexander Zverev squeezes a forehand past Carlos Alcaraz on the run, and then produces an awkward return to reach 15-30.

A chance, or half of one at least, but Alcaraz swings the game in his favour with an ace before another booming first serve gets him over the line.

Just like that, the pressure is back on Zverev.

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Alexander Zverev has to just keep in touch and hope for a dip in Carlos Alcaraz's level at some point, and he continues to do just that.

An ace seals a hold to 15. That's just one point against serve in four games now. Heading for another tie-break, perhaps?

Carlos Alcaraz edges ahead on the ace count with his seventh of the contest, and adds an eighth as another service game is settled without reply.

Another step closer.

Alexander Zverev has not done an awful lot wrong so far and responds to Carlos Alcaraz's love hold with one of his own. Efficiently done.

You'd be forgiven for forgetting that it's 30C out there with the way that Carlos Alcaraz continues to sprint around the place.

The Spaniard completes a clean game with a forehand winner before taking a seat in the shade, potentially just four games from the final.

Alexander Zverev hammers in a forehand for game points, but he's undone by Carlos Alcaraz in a rally which, in truth, he really should have finished off.

Will that prove costly? It's frustration for Alcaraz as he nets a forehand and lets Zverev off the hook.

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Alexander Zverev gets the better of Carlos Alcaraz to set up an early break point, but it's short-lived encouragement as Alcaraz closes out the game with an ace three points later. The German has to be taking any opportunity that comes his way now.

Two hours on the clock. Two sets on the board for Carlos Alcaraz.

Does Alexander Zverev have a fightback in him?

Jannik Sinner and Novak Djokovic will be hoping he can tire out the world number one a little bit more.

From 5-2 down in the second set, Carlos Alcaraz edges the tie-break to move within one set of the Australian Open final.

He has simply risen to the key moments better than Alexander Zverev in an otherwise tight match so far.

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It's 46 points apiece in set two as Alexander Zverev again holds his serve to move 5-4 up in the tie-break.

That tells you all you need to know about how close this semi-final remains.

But it will be Carlos Alcaraz who gets a first set point here as Zverev sends a volley wide...

Alexander Zverev ensures he keeps his nose in front with a couple of big first serves.

Carlos Alcaraz responds to his opponent's power with a delicate drop shot to level at 3-3, before finishing off the next point after dragging Zverev forward with another finessed touch over the net.

Nobody is blinking just yet.

Carlos Alcaraz has won all three tie-breaks he's played in Melbourne so far this year, while Alexander Zverev has lost two of the three he has contested.

The third seed gets up and running with the opening point, but Alcaraz responds with a backhand winner before Zverev sends a return long.

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Shotttt! Having found the line with an excellent cross-court backhand on his opening point, Carlos Alcaraz treats the crowd to a marvellous drop shot volley as he quickly dismisses any sense of pressure on this game.

A love hold. To a tie-break we go!

Well played! Alexander Zverev battles his way to a hard-earned hold of serve to guarantee himself at least a tie-break.

Both players head into the shade at the change of ends for brief respite from the baking heat, now above 30C.

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Alexander Zverev does well to wrest control of a point as Carlos Alcaraz continues to close down absolutely everything, eventually saving the first break point at the net.

Dismissing the second with an ace, the German moves to game point only for Alcaraz to sweep a two-handed backhand down the line.

More celebrations from Carlos Alcaraz as he drives in a forehand to claim the opening point on Alexander Zverev's serve.

The German mishits a forehand for 15-30, before Alcaraz turns defence into attack to pop in a volley for two break points.

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Carlos Alcaraz kept calm and knew Alexander Zverev might offer him an opportunity. The German's body language hasn't been great, despite having held a lead in the set, constantly chuntering to his team and at times distracted by issues with his racquet.

Alcaraz shakes his fist in the direction of his team as he celebrates restoring parity at five games apiece. You'd back him to go on and take this now.

Alexander Zverev saves the first break point with a hefty first serve, but Carlos Alcaraz drives a forehand into the back of the court to overwhelm the German on the second!

Back on serve in set two.

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