Stefanos Tsitsipas said two-week ATP Masters 1000 events result in a drop in quality as players do not get enough time off for recovery or the intense training needed to stay in shape over a long season.
Five Masters tournaments currently stretch over two weeks but earlier this year the ATP said that from 2025, seven of the nine events would now be held across 12 days each. That decision, however, did not go down well with players.
Tsitsipas was responding to former player Andy Roddick who said on his podcast that two-week Masters events are "so stupid" as more players seem to get injured when a week-long event would have allowed them to build their bodies up during off-weeks.
"The two-week Masters 1000s have turned into a drag. The quality has definitely dropped. Players aren't getting the recovery or training time they need with constant matches and no space for the intense work off the court," Tsitsipas said on X.
"It's ironic that the ATP Tour committed to this format without knowing if it could actually improve the schedule, but the quality likewise. Paris got it right, done in a week. Exciting and easy to follow. Just how it's supposed to be.
"If the goal was to ease the calendar, extending every 1000 (Masters) to two weeks is a backwards move. Sometimes, it feels like they're fixing what wasn't broken."
Reuters has contacted the ATP for comment.
Tsitsipas is not the first player to criticise the ATP, with four-times Grand Slam winner Carlos Alcaraz saying that the tight tennis calendar makes it difficult to stay motivated throughout the year and increases the risk of injuries.
"It is difficult. Sometimes I didn't feel motivated at all," Alcaraz said. "The calendar's so tight. A lot of tournaments ... not as (many) days off as I want."
Alexander Zverev said earlier this year that the two-week Masters events were great for players ranked between 50 and 100 in the world because they get a chance to play in a main-draw event, but the schedule was not ideal for top-10 players.
"Yes, you do get told you have a day in between (matches), you don't have to play every day. At the end of the day that's not resting," Zverev said ahead of the Rome Masters, which was a two-week event.
"Resting is when you're spending time at home, when you're sleeping in your own bed, maybe with your family, maybe with your dogs, maybe with your kids... That's what resting is.
"If you're at a different place, that's not resting. If you're going deep in events... if you're trying to make semifinals or finals of every event, you're just away a lot longer and you have to work a lot more. It's as simple as that."