Beijing, China - Hardly any professional tennis players support shortening men's Grand Slam matches, world number two Alexander Zverev said on Thursday, coming out strongly in favor of the "history" behind the format.

Some around the sport, including the chief executive of the organizing body that runs the Australian Open, have suggested in recent weeks that the four majors may eventually explore cutting early-round matches to the best-of-three sets from the current best-of-five.

Proponents argue the change would help audiences, particularly younger ones, engage better with a sport that can run to several hours in a tightly contested five-set match.

But Zverev shot down the idea at the China Open on Thursday, defending the format by saying: "It's history."

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"It's the toughest thing to win in our sport because we play best-of-five sets," the reigning French Open and US Open champion said.

"It's physically one of the most extreme things that you can go through."

Zverev played two five-setters en route to his US Open win, ending his first and second rounds well past midnight.

"I don't know a single player who would like to play best-of-three sets," the 29-year-old German said.

"Maybe Novak [Djokovic] wants to play best-of-three because, of course, he's getting a bit older now," he joked. "But I think if you had asked him this 10 years ago or 15 years ago, for sure not."

Djokovic (39) is a 24-time Grand Slam champion but a record 25th has eluded him so far.