CHICO, Calif. - Jose Canseco wrote the book that helped persuade baseball to toughen its steroids policy, and he insists there’s much more damaging information to come.

“I think what we’re seeing is just the tip of the iceberg,” Canseco said Monday, about five hours before he took the field for the first time with the San Diego Surf Dawgs in the independent Golden Baseball League. “I know for a fact that’s what we’re seeing.”

Canseco received a smattering of boos and cheers before the game when he was announced as the designated hitter against the Chico Outlaws, then again when he stepped into the batter’s box leading off the second inning.

Canseco, who said it had been at least four years since he last swung a wooden bat, struck out three times and was hit by a pitch in the Surf Dawgs’ 4-3 victory. The game drew 4,501 fans for the largest crowd ever to watch a game in Nettleton Stadium.

“I don’t know right now how to attack a breaking ball,” he said while fireworks went off behind him. “The pitchers have the upper hand. It will take a week or so. I’ve struck out three times in the big leagues when hitting hot as ever and come back the next day and hit a home run.”

He struck out swinging on four pitches leading off the second and again in the third on five, getting razzed in the process.

“Juiced!” one fan hollered, a reference to his book. “That’s not a big league pitcher, Jose,” another man yelled. Canseco was plunked on his left side by right-hander Nick Singleton in the fifth.

The crowd clapped when he finally made contact in the seventh, fouling off a pitch moments before he struck out for the third time. Some fans even watched from the roof of an apartment complex beyond the wall in right-center.

Earlier, Canseco called Major League Baseball “the mafia” for the way it has handled the game’s steroids scandal and suggested that the sport will discipline only certain players and might even hide the truth when it comes to big-name stars and positive tests.

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He plans to fight baseball to bring out the truth.

“They’re mafia, point blank, they’re mafia,” Canseco said. “I don’t think Major League Baseball is enthused about finding out the truth. There needs to be a major cleanup in Major League Baseball. I think they are treading on very thin ice, and (commissioner) Bud Selig has to be very careful what he’s doing because his job is on the line.”

When contacted about Canseco’s comments, baseball spokesman Pat Courtney said, “We wouldn’t comment on anything he said.”

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One day after his 42nd birthday, Canseco showed up at the ballpark tanned and toned with his short, black hair slicked back. He sported tight jeans and a black button-down shirt, with several of those buttons open, exposing his muscular chest. And he noted that years of steroids use has helped slow the aging process for him. He weighs 230 pounds — down significantly from his playing weight of between 255 and 260.

Canseco carried a fancy, red duffel bag when he made his entrance into the modest, 4,100-seat ballpark on the campus of rural Chico State University, some 170 miles north of the San Francisco Bay area. A sellout crowd turned out.

The former slugger — he has 462 career home runs — was back in professional baseball for the first time since finishing his 17-year major league career with the Chicago White Sox in 2001. Canseco signed with the Surf Dawgs last week for the remaining two months of the season, set to earn the league’s maximum salary of $2,500 a month. He even plans to pitch, featuring a knuckleball, and threw a bullpen session before Monday’s game.

It is unclear when Canseco might take the mound.

“Will it be with a one-run lead in the ninth? No,” Surf Dawgs manager Terry Kennedy said.