Watched under the roof of Centre Court by Rain Man star Dustin Hoffman amid a downpour outside, Alcaraz offered his best marathon man impression, getting stronger as a hugely entertaining match progressed before eventually prevailing 5-7 6-2 4-6 7-6 (7-2) 6-2 in three hours 50 minutes.
But there was a genuine scare for the holder, who had a strangely sluggish afternoon against his great American friend until the real danger came when he was two sets to one down and 0-30 down on his serve at 4-4 in the fourth.
Frances Tiafoe played some brilliant tennis before succumbing. (AP PHOTO)
Just as at the 2022 US Open, when the pair enjoyed an epic semi-final, Alcaraz found his brilliant best to prevail, winning the next four points, climaxed by a 130mph ace.
That year, he went on to win his first grand slam title and the form he demonstrated over the denouement of the fourth set and throughout the fifth suggested he will still be the man to beat if he can find that stellar level for longer stretches.
"I suffered a lot of difficult moments in the fourth set, and was thinking 'fight one more ball'. In the tie-break, I tell myself I have to go for it. If I lose it, I lose it," the 21-year-old explained to the crowd afterwards.
It certainly may have got easier for the young champion when 26-year-old Tiafoe, wearing a knee support following the sprained right knee ligament he had suffered at Queen's Club, seemed to exacerbate the injury when slipping and falling awkwardly in the tie-break.
Dustin Hoffman was just one who enjoyed the Hollywood entertainment on Centre Court. (AP PHOTO)
Having rescued that situation, Alcaraz then relaxed and started to pull out all the most entertaining stops in the decider, finishing the late super show with the most delicate of backhand drop shot winners.
But Tiafoe, who has had a poor season, dropping down the rankings to 30 after being in the top 10 this time last year and complaining about losing to "clowns", turned on one of his best displays for a long time to largely outplay the curiously subdued Alcaraz for much of the first three-and-a-half sets.
It was 49 years ago to the day that Arthur Ashe had become the first black man to win Wimbledon, and Tiafoe, whose parents are from Sierra Leone, was playing as if he believed he could follow in the late-great player's footsteps.
But once Alcaraz discovered his mojo, there was only going to be one winner as the third seed set up a last-16 clash with either American Brandon Nakashima or French 16th seed Ugo Humbert.
Jannik Sinner switched to cruise mode as the world No 1 breezed past unseeded Serb Miomir Kecmanovic 6-1 6-4 6-2 for a place in the fourth round.
After his dogfight with fellow Italian Matteo Berrettini ended shortly before the 11pm local curfew on Wednesday, the 22-year-old wasted little time under the roof on Centre Court, winning in just one hour 36 minutes.
Sinner said: "I'm very happy about my performance today. I felt like I was hitting the ball with good pace. I'm very happy about that."
On another wet day at this rainy Wimbledon, with two long interruptions to play on the outside courts, 33-year-old Grigor Dimitrov, the 10th seed, got the job done quickly in a battle of the veterans with 37-year-old Gael Monfils, winning 6-3 6-4 6-3.
Queen's Club champ Tommy Paul, the 12th seed, also looked good as he continued his brilliant grass-court summer by beating 23rd seed Alexander Bublik 6-3 6-4 6-2.
