Both players avoided the fate of Australian Open champion and sixth seed Madison Keys, who joined the mass exodus of top seeds.
It is only day five of Wimbledon but just four of the top 10 women’s seeds remain, with half of the men’s top 10 also ousted.
Men’s second seed Alcaraz eventually overcame German world number 125 Struff 6-1, 3-6, 6-3, 6-4 to stay on track for a third straight Wimbledon crown.
But the Spaniard will have to cut out his errors if he is to become just the fifth man in the Open era to perform that feat.
“I knew it was going to be really difficult. I had to be really focused. His game suits the grass with the big serves,” said the 22-year-old.
“It’s stressful. To be honest, I was suffering in every service game today, 0-30, break points down.
“I’m really pleased that I was fighting, running for every ball and making great shots.”
Alcaraz, watched by former England captain Gary Lineker and former world heavyweight champion Anthony Joshua, made 28 unforced errors in an inconsistent display on Centre Court.
But he conjured enough moments of magic to eventually subdue his opponent and book his place in the fourth round, where he will meet Russia’s Andrey Rublev.
Alcaraz is yet to show his best form after being pushed to the brink in a five-set win over 38-year-old Italian Fabio Fognini in the first round while he looked below his best again against British amateur Oliver Tarvet.
The women’s draw is bereft of star names after the departure of a succession of top players.
Keys’ 6-3, 6-3 defeat by Germany’s Laura Siegemund means only world number one Sabalenka is still alive at the All England Club out of the top six women’s seeds.
Coco Gauff, Jessica Pegula, Jasmine Paolini and Zheng Qinwen have already fallen by the wayside.
Sabalenka, last on Centre Court, refused to be cowed by former US Open champion Raducanu, who fed off the energy of a partisan crowd to produce an electric performance under the roof.
But the powerful Belarusian won the big points, saving a set point in the first set and staying strong in the second to beat her 40th-ranked opponent 7-6 (8/6), 6-4.
Sabalenka is a three-time Grand Slam champion but has never been beyond the semi-finals at Wimbledon.
“I had to fight for every point like crazy,” said Sabalenka, who was impressed by the volume of support for Raducanu.
“What an atmosphere,” she said. “My ears are still hurting, honestly. It was super loud. Every time you were cheering her, I was trying to tell myself to just pretend that you were just cheering for me. I had goosebumps.”
Earlier at the All England Club, Japan’s four-time Grand Slam champion Naomi Osaka lost in three sets to Russia’s Anastasia Pavlyuchenkova.
Osaka has not reached the fourth round of a Grand Slam since she won the Australian Open in 2021 but is still hungry for success.
“I feel like while I still have the opportunity to try to do it, I want to, even though I get very upset when I lose, but I think that’s my competitive nature. That’s also the younger sister syndrome,” she said.
There were also wins for Britain’s Sonay Kartal, 13th seed Amanda Anisimova and Elise Mertens.
US men’s fifth seed Taylor Fritz avoided a third straight five-setter, beating Spain’s Alejandro Davidovich Fokina 6-4, 6-3, 6-7 (5/7), 6-1.
Britain’s Cameron Norrie saw off Italian Mattia Bellucci in straight sets to qualify the quarter-finals for the first time since 2022, when he reached the last four.
Highly promising Brazilian teenager Joao Fonseca was ousted by Chilean qualifier Nicolas Jarry.
It took US men’s 10th seed Ben Shelton just 71 seconds to complete his second-round match, sealing a 6-2, 7-5, 6-4 win against Australia’s Rinky Hijikata after the match was halted on Thursday due to failing light. (AFP)
