NEW YORK — Already the highest-paid player, Alex Rodriguez wanted to prove himself one of the greatest. Instead, he wound up atop another list: the highest-profile player to confess to cheating in baseball's steroids era.

The All-Star third baseman, responding to a weekend Sports Illustrated report that he flunked a drug test, told ESPN yesterday he used banned substances while playing with the Texas Rangers from 2001-03 to justify his 10-year, $252 million contract.

"Back then it 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, you know, I was worth, you know — and being one of the greatest players of all time."

He said he didn't do it before then and quit during spring training in 2003, before the first of three AL MVP seasons, because "I've proved to myself and to everyone that I don't need any of that." He was traded to the New York Yankees before the 2004 season, and said he hasn't used it since.

The admission came two days after Sports Illustrated reported on its Web site that Rodriguez was among 104 names on a list of players who tested positive for steroids in 2003, when testing was intended to determine the extent of steroid use in baseball. The results weren't subject to discipline and were supposed to remain anonymous, but were seized by the government in 2004 and remain under seal.

"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 said.

"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."

In his first prime-time news conference, President Obama called Rodriguez's admission "depressing" news.

"And if you're a fan of Major League Baseball, I think it tarnishes an entire era, to some degree," Obama said. "And it's unfortunate because I think there were a lot of ballplayers who played it straight."

Rodriguez said part of the reason he started using drugs was the heat in Texas.

"Can I have an edge just to get out there and play every day?" he said to himself. "You basically end up trusting the wrong people. You end up, you know, not being very careful about what you're ingesting."

Though Rodriguez said he experimented with a number of substances, he never provided details.

"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."

SI reported Rodriguez tested positive for Primobolan and testosterone.

He said he stopped using during spring training 2003, when he sustained a neck injury. It was just as baseball started its drug-testing survey. It was only in 2004 that testing with penalties began.

During those three seasons, Rodriguez led the American League in homers each year and averaged 161.7 games, 52 homers, 131.7 RBIs and a .615 slugging percentage. In the other 10 full seasons of his career, he averaged 149.2 games, 39.2 homers, 119 RBIs, and a .574 slugging percentage, according to the Elias Sports Bureau.

"This is three years I'm not proud of," Rodriguez said.

Rodriguez's admission was in stark contrast to the denials of Bonds and of Clemens, Rodriguez's former Yankees teammate.

Bonds, a seven-time MVP, is scheduled for trial next month on charges that he lied when he told a federal grand jury in 2003 that he never knowingly used performance-enhancing drugs. Another federal grand jury is considering whether to indict seven-time AL Cy Young Award winner Clemens on charges he lied when he told a congressional committee last year that he never used steroids or human growth hormone.