Kevin Mitchell steps up to the plate and squares his massive shoulders, ready for battle. His eyes narrow as the pitcher blazes a fastball by him. When Mitchell takes a powerful cut at the next pitch and misses, his expression darkens and his tiny facial scars stand out more clearly. Kevin Mitchell is enraged. "I get two strikes on me and I tell myself, 'The pitcher, he's trying to take something from me,' " he says. "I'm ready to fight him."

It is a visceral response he learned years ago, in the days when he roamed his San Diego neighborhood with a gang called the Pierules. But these days the 5'11", 210-lb. left fielder for the San Francisco Giants is putting his anger to more profitable use. Just two months into the season, he was leading the major leagues with 22 home runs—three more than he hit all last season—61 runs batted in and a slugging percentage near .715. Partly as a consequence, the Giants are sitting at the top of the National League's Western Division. Says Giants general manager Al Rosen: "Kevin Mitchell is one of the most pleasant surprises I've had all season."

Mitchell's success represents a victory over private demons that have plagued his baseball career since the New York Mets first plucked him from the streets of San Diego to join their organization in 1980. "He was a tough kid," says Mets hitting coach Bill Robinson. "He had talent and a terrible attitude." Even in 1986, when Mitchell was enjoying a successful rookie major-league season, his behavior was getting him in trouble. In the clubhouse he was a prankster, torching teammates' shoes and cutting the sleeves off their expensive suits. On the field he was a brawler, twice drawing fines for fighting. The Mets clearly considered him expendable when they sent him to San Diego in 1986 as part of a five-player trade for slugger Kevin McReynolds. "I didn't listen," says Mitchell, 27, of his time with the Mets. "It was the way I grew up. I was always protecting my back, always threatening to go home."

Unfortunately, home, the tough Southeast San Diego neighborhood, had always been the source of his troubles. His parents broke up when he was 2, and three years later his mother sent him to live with his grandmother Josie Whitfield. The move proved fortuitous, since Whitfield, now 67, was a baseball fan who encouraged Kevin to play Little League. As he grew older, though, the streets seemed more glamorous. Mitchell dropped out of high school and spent four years among the Pierules, doing "a lot of bad stuff," as he puts it. He saw his share of bad stuff as well: In 1979 his brother, Donald, 16, was killed in a gang fight. For his part, says Kevin, he acquired a useful reputation for being able to knock people out with one punch.

Through it all, he kept playing baseball, and in 1980 he signed with the Mets. When he was traded back to San Diego six years later, he was not pleased. He moved in with Josie, who ran interference when old friends came calling. But just living in the neighborhood took its toll. "I get evil every time I go back there," Mitchell says.

Then, on July 4, 1987, Mitchell was traded again, this time to the Giants. "I had been traded two times and that was tough," he says. "I called my grandmother and told her I was coming home for good." Josie put her foot down. "I said, 'Kevin, look where you came from and how hard you worked. That's your gift. Why give it away?' He didn't say too much."

He also didn't quit. After moving to San Francisco, he came into his own. In his first game for the Giants, he hit two home runs, and this season he has been a revelation, joining the ranks of the game's premier sluggers. He sings when he's out in the field now, and no one is complaining about his attitude. "He's a quick learner," says batting coach Dusty Baker. "I never have to tell him anything twice."

Mitchell still lives in San Diego, but in a house across town from where he grew up. He has no girlfriend at the moment, and he finds himself back in the old neighborhood frequently, visiting Josie or talking to the kids at the local youth center. Though he shrugs off questions about his newfound maturity, he believes "being around good people"—like his sometime mentor, Willie Mays, and Giants manager Roger Craig—may have had something to do with it. Mitchell plans to be one of those people himself.

"Ain't no telling where I would have gone without baseball," he says. "I'd probably be in jail or somewhere dead. Everyone in my neighborhood thought I was going to be the bad guy, because I was always in trouble and in the gang fights. But now kids can see me and say, There's something else we can do. Just look at Mitch.' "

—Susan Reed, Dianna Waggoner in San Francisco