Nick Kyrgios has joked Rafael Nadal must be missing something after the 14-time major winner tipped him for big things in the coming years.
The controversial world number 13 endured a tumultuous year, pulling out of Rio 2016 after a run-in with the Australian Olympic Committee before receiving an eight-week ban from the ATP after an accusation of tanking at the Shanghai Masters.
Kyrgios' ban is reported to have been cut after he agreed to enter into a "plan of care", but criticism of his actions and attitude has been widespread.
After the 21-year-old retired from his third-round match against Illya Marchenko at the US Open, John McEnroe, commentating on the match for ESPN, said: "Nick Kyrgios, if you don't want to be a professional tennis player, do something else. He's hurt because he's not training enough."
However, Nadal has backed the Australian to start making a name for himself in 2017 and believes he we will challenge for major titles in the future.
"Nick Kyrgios is already at the top. [He is] a player who has unbelievable potential. He has to focus on himself and can become world number one and win a grand slam," the Spaniard is quoted as saying at a recent promotional event in Spain.
Kyrgios then posted a link to Nadal's remarks on his Twitter account, adding the comment: "I guess Nadal doesn't understand that I'm a waste of talent."
Kyrgios won three titles in 2016 as he rose from 42nd in the rankings to finish the year in a career-high position.