Giambi, the New York Yankees' first baseman, has been linked to steroid use. He testified before a San Francisco grand jury investigating Victor Conte and his Bay Area Laboratory Co-Operative.
The San Francisco Chronicle has reported that Giambi told the grand jury he had used steroids.
"When I went into the grand jury I told the truth," Giambi said Thursday. But he said for legal reasons he did not want to say more.
"Everybody makes mistakes and hopefully you'll always look for that second chance," he said. "Hopefully people will find in their heart to give me a second chance."