There's no doubt that tennis is one of the toughest sports in the world as Nick Kyrgios advocated for it recently.
There is no other sport in the world that can make two people play each other for 11 hours and 5 minutes over the course of three days as John Isner and Nicolas Mahut did at Wimbledon in 2010. Moreover, it's quite common that tennis matches last longer than four or five hours, and with many sports having a scheduled time limit, it's really difficult to compare.
Jon-Bernard Kairouz, who Kyrgios recently talked to in an interview, shared a video on his Instagram, explaining why rugby is the toughest sport in the world and comparing it to sports such as basketball. Kyrgios, who noticed the video, shared it on his stories, adding a caption stating:
"Tennis is by far the toughest sport in the world. I'm not even kidding."
The Australian then also shared highlights from his match against Roger Federer, and added: "Anyone who thinks tennis is easy, goodluck. Match went for about 3 and a half hours."
But in the comments, Kyrgios also explained why he thinks that tennis is the toughest sport, and it would be interesting to see him join the conversation, as his points were very clearly argued. He stated:
"Going on the road for 7-8 months at a time, week in week out different country. Could play up to 4-5 hours at a time. Involves, physicality, mental capacity, tactical awareness, all alone on an island, no teammates and no coaches. No scheduled or exact time to start or play, have to be able to back up day after day after day. Please let me in on this conversation."
Responding to some of the comments, the 2022 Wimbledon finalist later added:
"If you all think NRL (National Rugby League) requires more than say what Roger Federer or Novak Djokovic has had to put together is insane..."