His admission came two days after Sports Illustrated reported he tested positive for steroids in 2003, one of 104 players who tested positive during baseball's survey testing, which wasn't subject to discipline and was supposed to remain anonymous.
"And I did take a banned substance and, you know, for that I'm very sorry and deeply regretful. And although it was the culture back then and Major League Baseball overall was very - I just feel that - You know, I'm just sorry. I'm sorry for that time. I'm sorry to fans. I'm sorry for my fans in Texas. It wasn't until then that I ever thought about substance of any kind, and since then I've proved to myself and to everyone that I don't need any of that."
The 33-year-old All-Star third baseman was regarded by many in baseball as the most likely to break Barry Bonds' record of 762. He's already 12th on the career list with 553 homers, 209 behind Bonds.
Alex Rodriguez hit 52, 57 and 47 homers in his three seasons with the Rangers, winning the first of three AL MVP awards during his final season with Texas, where he received a $252 million, 10-year contract in December 2000.
"Back then it was a different culture. It was very loose. I was young. I was stupid," Rodriguez said. "I was naive, and I wanted to prove to everyone that, you know, I was worth, you know - and being one of the greatest players of all time."
He joined Jason Giambi and Andy Pettitte among All-Star players who have confessed to using performance-enhancing drugs. Many other players have denied any use.
Bonds, a seven-time MVP, is to go on trial next month on charges he lied when he told a grand jury in 2003 that he never knowingly used performance-enhancing drugs.
Roger Clemens, a seven-time AL Cy Young Award winner, is under investigation by a federal grand jury which is trying to determine whether he lied when he told a congressional committee last year that he never used steroids and human growth hormone.
SI.com reported Rodriguez tested positive for Primobolan and testosterone.
"It was such a loosey-goosey era. I'm guilty for a lot of things. I'm guilty for being negligent, naive, not asking all the right questions," Rodriguez said. "And to be quite honest, I don't know exactly what substance I was guilty of using."
Monday's ESPN interview directly contradicted a December 2007 interview with CBS's "60 Minutes," when Rodriguez said, "No" when asked whether he's ever used steroids, human growth hormone or any other performance-enhancing substance.
On Friday, Rodriguez is still expected to attend an event at the University of Miami, which is renaming its baseball field in his honor.
He gave $3.9 million to the school in 2003, the largest gift ever to the Hurricanes' baseball program and money that provided much of the resources needed for renovating the existing on-campus stadium. In return, the baseball complex will be called Mark Light Field at Alex Rodriguez Park.
Despite the scandal, the facility will continue to bear Rodriguez's name, a university official said Monday. The official spoke on condition of anonymity because of the matter's sensitive nature.
Miami baseball players and coaches were not available for comment, spokesman Mark Pray said.
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