Upon hearing the news that his friend and business partner, Lance Armstrong, admitted to doping after years of denying the allegation, Agassi was speechless.

The 42-year-old, Armenian-American, who co-founded a philanthropic organization with Armstrong, along with other athletes, such as Muhammad Ali, women's World Cup winner Mia Hamm and NBA champion, former Miami Heat and Georgetown University center, Alonzo Mourning was 100 percent sure that Armstrong was innocent.

According to a report on reuters.com, Agassi said, "my reaction to it is the same as everybody. It was shock, hard to stomach, sadness, disappointment. I think 'anger' is a fair word."

Adding, "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."

Agassi, who in his autobiography, "Open," released in 2007, admitted to "light" drug use during his playing career believes that, in comparison to cycling, tennis is a somewhat clean sport and he can't imagine any tennis player being able to cheat on the massive level that Armstrong admitted.

"It's a sport where I wouldn't know how to get away with that level of cheating. It's a year round sport. It's an out of body governance, 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 stated.

He actually feels that admitting his own wrongdoings on and off the court has helped tennis pursue more effective drug testing.

"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. That, to me, is a great thing."

For tennis, Agassi wants officials to expand testing. That way the sport isn't bombarded by claims of hiding the extent of any problem.

"Anything that can protect the integrity of the sport, and those that aren't cheating should absolutely be considered," he added.

"The more the better as far as I'm concerned. It's sad to watch people who may question things for those that worked pretty darn hard. Describing a problem is a heck of a lot easier than solving it, is one thing I've learned. Let's always have the discussion of making it more comprehensive."