Andre Agassi says many players have sought his advice over the years, but the nature of Novak Djokovic's quest to return to the summit of men's tennis convinced him to coach the former world number one.
The French Open has seen Agassi, an eight-time grand slam winner, begin working with the Serbian, who lost top spot in the rankings to Andy Murray in November and has struggled to produce his best form since a surprise early exit from Wimbledon last year.
Djokovic parted company with his previous 'supercoach' Boris Becker a month after being toppled by Murray and in May he surprisingly dismissed his remaining staff, including long-term mentor Marian Vajda, in a move he described as "shock therapy".
Speaking to Omnisport in Paris, where reigning champion Djokovic has reached a difficult quarter-final against rising star Dominic Thiem, Agassi revealed the motivation behind his decision.
"I follow my instincts and heart in life," he said.
"He called, many players have called me over the years and I talk [with them] but his search is very personal, very intense and very easy to respect.
"To come here, to get to know him, to give me a chance to maybe help more, I've followed my instinct. For me, helping Djokovic, if I can, I think it's good for the game, I think it's good for everybody.
"It's not a paid job for me. I'm not here because I'm getting paid. I don't make those decisions in life any more. I'm here because I believe he deserves it, I believe it's good for the game to have him at his best. And I respect anybody that's looking for more from themselves."
Agassi has already confirmed he is willing to work with Djokovic at Wimbledon if required next month and the 47-year-old is enjoying the challenge of trying to bring out the best in the younger man, who already has 12 major titles to his name.
"I told him and I've told everybody, I am absolutely available to help him, where I can be of most help to him," he said.
"I think we're learning this still together. And that might mean grand slams, that might mean practice week.
"Wherever we both figure out I can be of most help, he has my commitment and effort and that's just how I like to do things.
"I like to either do it, or not. To find ways to be engaged again. This is a time in my life I wanted to see. I don't need to do it but I find myself interested when I'm doing it with the right person."