By Heather Haddon

Calling his decision to juice “immature,” Yankees star Alex Rodriguez appealed for understanding yesterday while detailing how a Dominican cousin injected him with performance-enhancing drugs.

Some New York fans said A-Rod deserved a second chance, but also lambasted his first news conferencesince confirming he used steroids during his Texas Rangers years.

“Who is he apologizing to?” asked Jeff Mayer, 33, of Astoria. “It’s not going to affect his salary, and other teams will still pay for him, so he’s not sacrificing anything.”

Flanked by Yankees general manager Brian Cashman and manager Joe Girardi, A-Rod read from a prepared statement and dramatically paused before thanking his teammates clustered to his right. The two-time MVP winner reveled new information about his use of illegal steroids since the news broke 10 days ago:• A Dominican cousin supplied and injected Rodriguez with an over-the-counter enhancer twice a month during the 2001-2003 seasons

• The drug was called “boli” or “bole” in the Dominican Republic

• Rodriguez stopped juicing because of a neck injury and Major League Baseball’s move to regularly test for steroids

• While playing for the Seattle Mariners, he also used an over-the-counter supplement now banned by the league called Ripped Fuel

• Rodriguez denied every using human growth hormone

Rodriguez would not reveal his cousin’s name. He said the drugs provided more energy, but was vague about the exact results. Rodriguez said he had “no regrets” at the time, but also called himself young and foolish.

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“Initially I was curious,” said Rodriguez, 33, speaking before 200 reporters gathered at Steinbrenner Field in Tampa. “I just gave it a try.”

Fan Carlos Alvarez didn’t think naivety flew as an excuse.

“He was young, but not oblivious to what’s right and wrong,” said Alvarez, 30, of Manhattan.

Rodriguez denied using performance-enhancing drugs for years, but Sports Illustrated reported he tested positive for Primobolan and testosterone during a 2003 round of anonymous testing.

A-Rod said other players did not influence his juicing, and that the secret stayed between him and his cousin.

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“He lost the love of the game and that’s why he did what he did,” said fan Jesus Acosta Jr., 26, of Manhattan.

Yankees historian Peter Golenbock thought the scrutiny of A-Rod would die once the season starts April.

“What’s important is what’s on the field, not what A-Rod did back in 2003,” Golenbock said from St. Petersburg.

Rodriguez said its up to others to decide if the stats from his steroid-abusing years should count toward his record. He repeatedly appealed for forgiveness from his teammates and fans.

“I’m here to take my medicine,” he said.

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(Andrew Breiner contributed to this story)