The sixth-seeded Zverev nearly took out Alcaraz, the 2023 Wimbledon champion, in straight sets when he found himself up 5-2 in the third, but Alcaraz stormed back to force a fourth set with a 7-6 (7-2) win.
The 26-year-old Zverev, who last made the Australian Open semifinals in 2020, attributed his third-set collapse to overthinking and getting ahead of himself against one of the world's best players.
The fourth set was a tight one, with Alcaraz threatening to force a fifth and deciding set. Both Alcaraz and Zverev broke serve before Zverev broke again to go up 5-4. He would close out his opponent with a service winner.
The stars align for Sascha in Melbourne ✨@AlexZverev returns to the AO semifinals and is one step closer to a maiden Grand Slam trophy ✨@wwos • @espn • @eurosport • @wowowtennis pic.twitter.com/WLYySu0iYz
— #AusOpen (@AustralianOpen) January 24, 2024
Daniil Medvedev will be Zverev's semifinal opponent, with Jannik Sinner taking on top-seeded Novak Djokovic on the other side of the bracket.
Zverev battled through an ankle issue that needed medical treatment before the start of the fourth set, but it did not slow him down to finish the job.
"I would much rather feel the way I'm feeling right now with, maybe, a bit of pain here and there and be in the semifinals than be at home right now and watch this tournament," Zverev said afterward. "I'm happy to be here and ready to get going."