Andre Agassi was shocked and saddened by disgraced cyclist Lance Armstrong's confession to using performance-enhancing drugs and the eight-times grand slam champion said tighter, more frequent dope testing procedures in tennis would be good for the sport.
The American, who co-founded a philanthropic organisation with Armstrong and other athletes like Muhammad Ali, women's World Cup winner Mia Hamm and NBA champion Alonzo Mourning, said he had been convinced of Armstrong's innocence.
"Well, my reaction to it is the same as everybody. It was shock, hard to stomach, sadness, disappointment. I think 'anger' is a fair word," Agassi told reporters at Melbourne Park on Friday.
"I was certainly one of those that flat out believed him that long period of time. The thought of it not being the case was unconscionable to me."
Armstrong, 41, admitted in an interview with Oprah Winfrey last week that he used performance-enhancing drugs and lied about it for over decade, finally owning up to being at the centre of one of the biggest drug scandals in world sport.
In 2007, Agassi and Armstrong were two of the founders of the organisation, Athletes For Hope, which helps educate professional athletes on how to raise money and the profile of charitable and philanthropic causes.
The 42-year-old Agassi, who admitted to recreational drug use in his autobiography "Open", said he felt that tennis was relatively clean and doubted anyone would be able to get away with the systemic level of doping that Armstrong admitted to.
"It's a sport where I wouldn't know how to get away with that level of cheating. It's a year round sport," Agassi said.
"It's an out of body governance, a third party governance. When last I played, it was comprehensive in the sense of nearly every tournament, nearly week to week, blood, urine, out of competition testing.
"I don't know how it's changed, but if it's stayed the same at least that's a good thing."
Agassi tested positive for methamphetamine during his career, but lied to ATP officials about how it got into his system, claiming he had consumed a drink spiked with the drug.
He felt that his own drug use, and how he avoided a ban, may have helped tennis in pursuing more vigorous drug testing programmes.
"You know, for their own reasons I might have played a part in it, for them going to WADA (World Anti-Doping Agency) and the governance that has no horse in the race," he said.
"That, to me, is a great thing.
"For me, it would have kept me from destroying a few years of my life. That's what I did to myself with the use of the recreational, destructive substance of crystal meth.
"It would have saved me on a lot of fronts."