"A lot of players feel like, okay, it is a good calendar. And a lot of players says that it's really tight and a lot of tournaments during the whole year," Alcaraz told Sportskeeda after defeating Ben Shelton at the Laver Cup earlier this week.
"I'm the kind of player who think there is a lot of tournaments during the year, mandatory tournaments, and probably during the next few years gonna be even more tournaments, more mandatory tournaments. So, I mean, probably they are going to kill us in some way," he added.
World number three Alcaraz has played 50 matches so far this season.
Other big names such as Alexander Zverev and Grigor Dimitrov have also criticized the lengthy schedule of ATP Tour.
Sinner was asked to comment on Alcaraz's opinion during his pre-game press conference at the China Open, and he said players are free to choose a schedule that fit them.
"The schedule is quite long obviously these years. But we players, we can still choose what to play and what not to play. Obviously we have some mandatory events," Sinner said.
"It is a very busy schedule this year; there are a lot of tournaments. You don't have to play a tournament. If you want, you can play. If not, you don't play. For example last year and also this year, I didn't play some tournaments because I wanted to practice. There are some choices behind this," he added.
Tennis has the longest season in sports, running from January to December, with the final event being the Next Gen ATP Finals. However, there are also long breaks between the majors, such as after the Australian Open or after Wimbledon. The end of the year is often filled with big events such as the U.S. Open, Masters 1000 series, ATP Finals and Davis Cup finals.
On Wednesday, Alcaraz, who is also in Beijing for the China Open, was asked about Sinner's statements in a press conference, and he
"I've seen and I've heard a lot of players complain about the schedule, about the calendar as well. I hear about in Jannik's press conference here, he talk about it a little bit," Alcaraz said.
Other star players such as Daniil Medvedev, Andrey Rublev and Dimitrov also participate in the China Open. After this tournament, they will come to Shanghai for the Masters 1000, joined by Novak Djokovic and Zverev.