A growing debate about player workload, late finishes and the demands of the calendar gathered momentum at the US Open last month after Ben Shelton ended Alcaraz's title defence in a quarter-final that finished at 3:33 a.m.
While the Spaniard has joined calls for measures to prevent matches spilling into the early hours, he said at the Japan Open on Wednesday that the answer was not to dilute the format that has long defined the sport's biggest prizes.
"The beauty of the Grand Slams is playing best-of-five sets. If we take away that and play best-of-three sets, we're killing the legacy of the Grand Slams and killing the Grand Slams," Alcaraz told reporters in Tokyo.
"We've been playing best-of-five sets in the Grand Slam since the very beginning, and I think that's what makes those tournaments different and special. I wouldn't touch anything from that and for me, it's okay to play best-of-five."
Novak Djokovic has previously proposed best-of-three matches in the initial rounds of Grand Slams, while new Tennis Australia chief Andrew Abdo said at last month's Sport NXT conference that the majors could explore alternative formats or scoring systems.
Abdo's comments were followed by a clarification from the Australian Open that while innovation was a part of the Grand Slam's DNA, five-set tennis was "here to stay" and it would reveal more ahead of the 2027 tournament.
Closer engagement with players
The four majors have nevertheless sought closer engagement with players through a newly formed Player Advisory Council, a forum to address their concerns over welfare and compensation after protests in recent months.
The Grand Slams have not formally announced the council's membership, though media reports say it features top players like Novak Djokovic, Elena Rybakina and Aryna Sabalenka, while Alcaraz and the top-ranked Jannik Sinner are not involved.
Rather than altering Grand Slam formats, Alcaraz said tennis should focus more on reducing the demands of the 11-month calendar after a season in which he was sidelined with a wrist injury for nearly five months before his return in New York.
Those concerns also feature prominently in the Professional Tennis Players Association advocacy group's class-action lawsuit against the sport's governing bodies.
"I've always said that it has to change," Alcaraz added, referring to the calendar.
"Playing a little bit less and not having that amount of tournaments in a row, week after week. So I definitely would change that."
The ATP did not immediately respond to an emailed request for comment outside regular business hours.
Its chairman, Andrea Gaudenzi, defended the crowded calendar last year, saying scheduling remains the players' choice and the tour was working to set clear incentives so the right number of matches were played across the season.