The balance of power between the two tennis titans of the age again shifted towards the Italian again on Sunday (Monday AEST), as he began the clay-court season by lifting his first big title on the red stuff while outplaying Alcaraz 7-6 (7-5) 6-3 at the Monte Carlo Country Club.
On Monday, Sinner will begin his third separate reign as world No.1, the fourth time the pair have grasped the honour from each other, and it sets the scene for another fascinating arm-wrestle on clay leading up to perhaps another French Open final classic at the start of June.
For once, unlike their last clay battle in that matchless 2025 Roland Garros five-setter edged by Alcaraz, this match didn't elicit the best of the colossal young duo, the windy seaside conditions knocking them off their game somewhat in front of Prince Albert and his VIP pals.
Not that the weary Sinner was complaining. "I don't know where to start, honestly," he spluttered.
"We came here just to win as many matches as possible, to get good feedback before other big tournaments coming up, but the result is amazing. Getting back to number one means a lot to me.
"Today wasn't a very high level from both of us, a bit windy and breezy, different conditions from the rest of the tournament ... but I'm very happy to win at least one big trophy on this surface, it means a lot."
He handled the conditions more convincingly as he prevailed in two-and-a-quarter hours for a fourth successive Masters 1000 title, having won in Paris, Indian Wells and Miami.
In January, Alcaraz's Australian Open title, coming after his US Open triumph, had underlined the tantalising prospect of a new long-reigning king at 22, but Sinner has been startlingly good since, winning the Indian Wells/Miami/Monte Carlo treble only ever previously achieved by Novak Djokovic.
Even Alcaraz recognised how monumental this was.
"It's impressive what you are achieving right now. Just one man in the Open Era did this, and you are the second," the Spaniard told his 24-year-old rival, with whom he has the most friendly if intense of rivalries, at the presentation ceremony.
"It's something incredible. I just experienced how difficult it is to make that happen."
After picking up his eighth Masters crown overall to regain his No.1 spot after a five-month hiatus, Sinner slumped to his haunches and looked down, clearly emotional about his achievement.
The last time they'd met was five months ago when Sinner won their ATP Finals title clash, but this wasn't a clash on that level, with 83 unforced errors, including 45 from Alcaraz's racquet, littering the show.
Still, Sinner always looked more composed in the big moments, producing first-serves throughout the opening tiebreak, while Alcaraz double-faulted on set point.
The Spaniard did strike back early in the second set to lead 3-1 with a couple of crowd-pleasing rapier returns, but Sinner ground him back into place, reeling off four-straight games to hand Alcaraz his first defeat after 17 consecutive wins on clay.
Just as Alcaraz had, it's now Sinner who looks unstoppable. He's now won 22 matches on the bounce at Masters 1000 level, and his head-to-head deficit against Alcaraz, which had begun to be a gaping problem, is now down to 7-10.
It's still those two -- and there's no sign of any let-up to encourage the rest.
