Andre Agassi and Steffi Graf
10/27/2009 AT 06:15 PM EDT
Tennis star Andre Agassi serves up a bombshell in his new memoir: In the late '90s he began regularly using crystal meth. "I can't speak to addiction, but a lot of people would say that if you're using anything as an escape, you have a problem," he tells PEOPLE.
Agassi's book, Open, details his descent into drug use, as well as his hair loss, his troubled marriage to Brooke Shields and the love he eventually found with his current wife, Steffi Graf.
Asked how he thought his fans would react if they found out he was using drugs, Agassi, 39, says: "I was worried for a moment, but not for long. ... I wore my heart on my sleeve and my emotions were always written on my face. I was actually excited about telling the world the whole story."
For Agassi's story in his own words – including his ambivalent attitude toward the sport that made him famous – read an excerpt from his book in the new PEOPLE, on newsstands Friday. An excerpt also appears in the new SPORTS ILLUSTRATED