BERKELEY — The boy wasn't allowed to play tackle football.
"My mom thought I was too small," he says. "She thought I'd get hurt."
No matter how long or hard he complained -- they always fell into the same argument -- she refused to give in.
So all the way through elementary school and into junior high, he played two-hand touch in the street, inventing games with his friends.
One of his favorites, "Juke 'em," sent a lone player twisting and dodging, trying to steer clear of everyone else.
"We took the concept of monkey in the middle," he says. "The person with the ball had to see how long he could last."
When seventh-ranked USC plays at No. 24 California on Saturday, if you watch Golden Bears tailback Jahvid Best closely enough, you might catch a glimpse of those childhood moves.
With quickness and swerve born on the blacktop, Best now ranks among the top backs in the nation, a Heisman Trophy contender accounting for better than 116 yards and two touchdowns a game.
Add to those numbers a touch of vengeance as Best and his teammates look to redeem themselves after a stunning, one-sided loss at Oregon last weekend.
"He's aggressive and elusive," USC Coach Pete Carroll said. "But it's really his extraordinary speed."
That speed was honed on the track, where Best found an outlet during all those years he wasn't allowed to play football.
As an elite junior sprinter, he won the 200 meters at the 2005 USA Track and Field Junior Olympics. Two years later, running for Salesian High in Richmond, Calif., he clocked a 10.31 to capture the state 100-meter title.
By that time his parents, David and Lisa, had relented, allowing Jahvid to put on a helmet and shoulder pads. The same school year he won the 100-meter championship, Best also gained a mind-boggling 3,325 yards and scored 48 touchdowns for Salesian.
Coach Jeff Tedford wanted him to play at Cal, just down the freeway, but had to wonder. On a recruiting visit, he asked Best which sport was truly in his heart, football or track?
"Track," Best said.
Such was the young man's potential that Tedford did not hesitate, rationalizing: "It said a lot about him, that he was being honest."
And running backs coach Ron Gould loved Best's speed so much, it did not matter that he had much to learn about the game.
"Alignment, assignment, tempo, pace," Gould said. "We had to mold him."
If anything, Best needed to slow down. He would hit the line before the big guys had a chance to make their blocks and cut too quickly, leaving himself off balance.
From the moment he stepped onto Cal's practice field, football became his passion -- track soon fell by the wayside -- and he learned to trust Gould's instruction.
After all, Cal had produced a string of backs -- J.J. Arrington, Marshawn Lynch, Justin Forsett -- who graduated to the NFL.
"As I started to understand, the game slowed down," Best said. "I could see things happen and anticipate."
He showed flashes of brilliance as a freshman, then became a starter last season and finished third in the nation with 1,580 rushing yards. Still, an old concern lingered.
By football standards, Best is on the small side, generously listed at 5 feet 10, 195 pounds.
A hip injury ended his first season a few games early and a dislocated elbow hampered him much of last fall. He missed both of the last two spring practices because of injuries and surgery to the elbow and a foot.
No wonder Lisa Best continues to worry.
"Football has always been such a physical game," she said. "Of course I'm fearful."
During one game, when her son's helmet kept popping off, she frantically sent text messages to the Cal trainers. It turned out that Best -- his first name combines the spiritual "Jah" with David -- insisted upon using a helmet that did not fit snugly.
Last season, when Best got leveled on a screen pass at Maryland, suffering a bruised sternum, Lisa sprang from her seat.
"I was able to get on the field," she said. "I snuck past security and went to the treatment room . . . they knew who I was."
Best insists that his injuries have been "freak accidents" and not indicative of any pattern. This summer, he added more than 10 pounds of muscle to his thin frame.
"I'm not worried about my durability at all," he said.
His coaches and teammates feel likewise. They prefer to talk about his dazzling skills.
Hardly a workhorse -- he shares time with sophomore Shane Vereen -- Best is more likely to hit with lightning strikes.
Tedford has a favorite: a reverse against UCLA last season when his tailback hopped over one tackler, then froze three more with a shimmy before accelerating down the sideline for a 34-yard touchdown.
Also last season, big plays added up to 311 yards against Washington and 186 yards against Miami in the Emerald Bowl.
This fall he quickly verified his status as a Heisman candidate with five touchdowns at Minnesota.