(espn) His voice shaking at times, Alex Rodriguez met head-on allegations that he tested positive for steroids six years ago, telling ESPN on Monday that he did take performance-enhancing drugs while playing for the Texas Rangers during a three-year period beginning in 2001. "When I arrived in Texas in 2001, I felt an enormous amount of pressure. I felt like I had all the weight of the world on top of me and I needed to perform, and perform at a high level every day," Rodriguez told ESPN's Peter Gammons in an exclusive interview in Miami Beach, Fla. "Back then, [baseball] was a different culture," Rodriguez said. "It was very loose. I was young. I was stupid. I was naive. And I wanted to prove to everyone that I was worth being one of the greatest players of all time. "I did take a banned substance. And for that, I am very sorry and deeply regretful." Major League Baseball had no comment Monday. Rangers owner Tom Hicks said Rodriguez's admission caught him by surprise. "I feel personally betrayed. I feel deceived by Alex," Hicks said in a conference call, according to The Associated Press. "He assured me that he had far too much respect for his own body to ever do that to himself. ... I certainly don't believe that if he's now admitting that he started using when he came to the Texas Rangers, why should I believe that it didn't start before he came to the Texas Rangers?" Rodriguez's admission comes 48 hours after Sports Illustrated reported that Rodriguez was on a list of 104 players who tested positive for banned substances in 2003, the year when Major League Baseball conducted survey tests to see if mandatory, random drug-testing was needed in the sport.