Bernard Tomic says he has never "really tried" throughout his tennis career, adding that he has probably been operating at "around 50%".
The Australian claimed he was bored during his straight-set defeat by Mischa Zverev at Wimbledon on 4 July.
A series of lacklustre displays has seen the 24-year-old drop from 17 in the world last year to 73.
"Tennis chose me. It's something I never fell in love with," Tomic told Australia's Channel Seven.
"Throughout my career I've given 100%. I've given also 30%. But if you balance it out, I think all my career's been around 50%.
"I haven't really tried, and still achieved all this. So it's just amazing what I've done."
'I'm trapped and I have to do it'
Tomic has won three ATP Tour titles and has earned almost £4m in career prize money, including £35,000 for his defeat by Zverev.
However, he has not won a tour title since 2015 and has struggled for form this year, winning just nine matches overall and losing in the first rounds at the French Open and Wimbledon.
When asked what advice he would give to aspiring tennis players, Tomic said: "Don't play tennis.
"Do something you love and enjoy because it's a grind and it's a tough, tough, tough life. My position, I'm trapped. I have to do it."
Tomic's previous controversies
Tomic was criticised for ruling himself out of the Rio 2016 Olympics because of an "extremely busy" schedule, a year after he was dropped by Tennis Australia - for a second time - from their Davis Cup squad.
He was left out in 2015 after accusing the governing body of abandoning him following hip surgery in 2014, but has since returned to the team.
Further questions were raised about his attitude when he held his racquet by the strings when facing match point in a Madrid Open match last year.
Tomic's career has also been affected by off-court controversy.
In July 2015, he was charged with resisting arrest and trespassing by police in the United States after refusing to leave a hotel room.
His father John was sentenced to eight months in prison for assaulting his son's training partner before the 2013 Madrid Open.