By SABC Sport
24th January 2024
The Wimbledon champion had been in excellent form in Melbourne and threatened a comeback after a slow start but it was Zverev moving through to the last four thanks to a 6-1 6-3 6-7 (2) 6-4 victory clinched at 1.19am.
In his seventh grand slam semi-final, Zverev will take on third seed Daniil Medvedev, who earlier battled past Hubert Hurkacz in five sets.
Alcaraz was heavily fancied to make it an all top-four semi-final line-up but he looked very tight at the start and Zverev took full advantage, barely missing a first serve and striking his groundstrokes with power and precision.
The German had faced a lot of off-court scrutiny regarding his forthcoming domestic abuse trial - he denies the allegations - but his ability as a tennis player was unquestionable.
Alcaraz improved at the start of the second set, finding some of the dynamic, all-court play that has made him such a fan favourite, but he could not take either of two break points in the sixth game.
He then found himself under more pressure in the following game and, after being given a time violation, he netted a forehand to drop serve again.
Alcaraz, who had comfortably beaten Zverev at the same stage of the US Open last summer, looked furious with himself but he could not conjure up any response as errors continued to flow from his racket.
The end seemed nigh when Zverev, who lost his only grand slam final to Dominic Thiem at the US Open in 2020, broke serve again to lead 3-1 in the third set.
But Alcaraz roused himself just in time to break the Zverev serve for the first time at 5-3 and then reeled off a string of seven absurd points to win the tie-break and take it to a fourth set.
The German received treatment for blisters on his foot and Alcaraz seemed to have the momentum but more errors helped Zverev break to lead 5-4 and this time he managed to serve it out, securing his first victory over a top-five opponent at a slam.
"When you're up 6-1 6-3 5-2, you start thinking," said Zverev. "It's not always helpful but I'm happy I got there in the end. I fought back quite well in the fourth set."
Earlier, Medvedev struggled in the heat of the day against ninth seed Hurkacz, who was looking to make the last four at a grand slam for only the second time.
The Pole twice fought back from a set down but Medvedev came out on top 7-6 (4) 2-6 6-3 5-7 6-4 after three hours and 59 minutes.
The Russian finished it off with a drop shot before blowing kisses towards his box.
Medvedev will now try to reach the final for the third time in four years, and he said: "I'm so destroyed right now. I was feeling very tired physically at the end of the second set already.
"In the fourth set, he played good, I wasn't beating myself up. I had no more concentration, I thought, 'I just have to try my best to do whatever I can. If I lose, I lose and I go home. It's OK'. I'm happy that like this I managed to win and I really liked the match point."
It was a back-and-forth contest throughout between the two big servers, who both move tremendously well for such tall men.
Medvedev edged the first set on a tie-break and looked to be in full control when, having dropped the second, he took the third and moved a break ahead in the fourth.
But Hurkacz, who had won his last two matches against the Russian and their only previous grand slam meeting at Wimbledon in 2021, did not allow his head to drop and levelled at 4-4.
It was now Medvedev under real pressure on serve, and Hurkacz clinched his opportunity to force a decider when his opponent sent a forehand long.
Medvedev had survived a five-setter in the second round, coming from two sets down to defeat Emil Ruusuvuori at nearly 4am.
And the third seed was not to be denied, a break in the seventh game proving the difference.