San Diego ? Mike Cameron always had a squeaky-clean image.

He was best-known for hitting four homers in a game in 2002 and for a frightening, face-to-face collision with a teammate in the outfield three seasons later. He was a family man, and his kids would hang out in the San Diego clubhouse when they visited from Atlanta.

A month after the Padres’ season came to a stunning end, they received another shock Wednesday when Cameron, their Gold Glove center fielder, was suspended for the first 25 games of next season after testing positive a second time for a banned stimulant.

Cameron filed for free agency a few hours later. The suspension certainly won’t help his market value in a year when All-Star center fielders Andruw Jones, Torii Hunter and Aaron Rowand also are on the market.

Cameron beat the commissioner’s office to the announcement, revealing the suspension during an interview on AM 1090, the Padres’ flagship radio station.

“The one thing I wanted to make sure was explained is, no steroids,” Cameron told the station. “I never took nothing like that before in my life. That would be 50 games, and that would affect me a whole lot more.”

Cameron, who turns 35 on Jan. 8, said he thinks he took a tainted supplement.

He later issued a statement through his agent, saying doctors for the players’ association helped him narrow down what triggered the positive test.

“After all of the analysis and testing, I can only conclude that a nutritional supplement I was taking was tainted,” he said. “Unfortunately, the actual supplement is gone, and therefore cannot be tested. Without the actual supplement in hand, the rules are clear, and I must accept the suspension.”

Players who initially test positive for a stimulant receive counseling. Suspensions begin only with a second positive test.

“Mike has been a valuable member of the Padres over the last two seasons who has been respected for his contributions on the field, his stature in the clubhouse and his involvement in the San Diego community,” Padres CEO Sandy Alderson said in a statement. “Accordingly, the Padres are extremely disappointed that Mike has tested positive for a stimulant banned by MLB’s drug policy.