Rafael Nadal revealed his battle against chronic pain but said his ambitions of winning another Grand Slam was very much alive as he formed a new partnership with Spanish coach Carlos Moya.
Injury-hit Nadal, 30, said he hadn't played without pain for years but that he remained optimistic of challenging for big titles again.
When asked if he was free of pain and injuries, the Spaniard smiled ruefully and said: "I am not injured, no. Pain-free is a long time ago."
Nadal hasn't reached a Grand Slam semi-final since 2014 but after lengthy discussion with his long-time coach, his uncle Toni Nadal, he hired fellow Spaniard Moya in December.
"I am not a person who takes decisions like this," Nadal said, clicking his fingers. "I need to talk. More than anything, you know, my uncle is my coach.
"He is a person that is decisive in my career, so I need to talk with him before taking any of these decisions. I will never take a decision like this if Toni is not happy with it."
He added: "He's (Moya) a person that I practised with during almost all my career since I was 15 until he retired... It's not a big deal, no? He is close to my house. He lives in Mallorca, too."
Nadal, the current world number nine, plays Germany's Florian Mayer in the first round on Tuesday and is seeded to meet top-rated teenager Alexander Zverev in the third round.
Last year, Nadal lost in the first round at Melbourne Park to compatriot Fernando Verdasco. But he said he wouldn't be playing if he didn't think he had a chance of lifting the trophy.
"If I don't believe that I can be competitive and when I say 'competitive', it's fighting for the things that I fought for during the last 10 years -- I will be probably playing golf or fishing at home," he said.
"I am being honest about this. If I am here it's because I believe... I can fight for the things that really motivate me."