Andre Agassi tells People magazine he used crystal meth periodically for "a year or so." In his upcoming autobiography, Agassi admits he used crystal meth in 1997 and failed a drug test a result he says was thrown out after he lied by saying he "unwittingly" took the substance. The eight-time Grand Slam champion tells People that he felt it necessary to be as candid as possible in the memoir. New excerpts published Friday reveal Agassi wore a hairpiece that nearly fell off at the 1990 French Open, became jealous during ex-wife Brooke Shields' appearance on "Friends," and how Shields put a photo of Steffi Graf now married to Agassi on the fridge for motivation to get in shape before their wedding.