How do you tackle Marcus Allen?

"I would let him get beside me, then jump on him. You don't try to take him head-on because most times he'll run through you. I mean, he runs crazy. You take him on, most times, you don't get him."

The analyst was Marcus Allen, laughing as he talked about why people have difficulty stopping him when he comes dashing out of Southern California's backfield.

This is not conceit. Just a matter of fact. And the ability to slip tacklers, avoid tacklers and run through tacklers has made him the favorite for the Heisman Trophy in what started out to be the Year of Herschel Walker.

"What an unbelievable back," said Notre Dame Coach Gerry Faust after Allen had gained 147 yards against his team Oct. 24. "We defensed him well. We were there, waiting for him. I've never seen a back take that kind of punishment and still keep coming back."

While Faust spoke, Allen was making some of his best moves of the year, ducking between equipment bags, naked bodies and reporters to get from the showers to his locker in the small visitors' dressing room at Notre Dame.

His forehead was purple from several bruises and he walked gingerly. But he also knew that his job was not finished when he left the field, that when you are the candidate, answering questions is almost as important as following your blockers.

Still, he stood in front of his locker, arms folded, and patiently discussed the game. When a microphone got too close for comfort, he didn't snap. "I talk better with room," he said softly. The microphone was backed away.

Room is not something Allen needs on the field. He is a quick back, but he also is a slasher, the kind who almost never goes down on the first hit. His teammates call him "Young Juice."

"We've had two kinds of backs here, the kind that pick their holes and the kind that attack," said Trojan Coach John Robinson. "Last year, Marcus picked his holes more. Now, he attacks, he's become an attacking runner. And, he's got that explosive ability."

Allen's statistics this year are astonishing. In nine games, he has rushed for more than 200 yards seven times. In the other two games, he gained 153 and 147 yards. He averages 217.5. He has rushed 1,968 yards, breaking Tony Dorsett's record of 1,948, with two games to go.

He will win the Heisman Trophy. For a USC tailback that is not unusual. But Marcus Allen is not your usual USC tailback.

He was recruited from Lincoln High School in San Diego as a defensive back. In high school, he played quarterback and defensive back. He was the player of the year in California and was heavily recruited. He narrowed his choices to USC and Oklahoma.

"I visited Oklahoma and really liked it," Allen said. "I guess (with) my dad being from Texas I could fit in with that kind of atmosphere, I have some of it in my blood. But in the end, I could remember watching SC in '67 and '68 when Juice (O.J. Simpson) was there. They were always my favorite team and he was kind of my role model."

Allen first met Simpson at a banquet shortly after signing with Southern Cal. The two became friends quickly and, today, Simpson is Allen's unofficial advisor.

When Simpson is away, Allen, who lives off campus in an Inglewood apartment, sometimes stays at Simpson's place. When Allen's car, a Datsun 280Z, was being repaired, he borrowed Simpson's Ferrari -- for three days. O.J. wasn't pleased.

Allen arrived at Southern Cal as a defensive back with a reputation as a vicious tackler. He lasted five days on defense.

"I looked at him for a couple of days and just said, 'He has to be around the football,' " Robinson said. "He didn't object when I suggested he move to tailback."

Allen readily admits to having daydreamed in high school of being the SC tailback, of thinking about following people such as Simpson, Mike Garrett, Anthony Davis and Ricky Bell into college football's No. 1 glamor position.

He played sparingly as a freshman, carrying the ball 31 times. With Charles White coming back for his senior season, Allen's sophomore year looked like another inactive one. Then Robinson came up with another suggestion: move to fullback.

"I said, 'Fine,' " Allen remembered. "I just wanted to play. I don't think I quite realized what I was getting into.

"I did a lot of blocking that season. Toward the end, I learned how to avoid the center of the line where it all piles up. All I wanted to do was survive. But in the end, it was a good experience I think."

It was also a good experience for White, who ran behind Allen and the USC line to the Heisman Trophy. Then he graduated and Allen was finally the tailback. More accurately, the tailback.

He rushed for 1,563 yards in 1980 in 10 games, averaging 4.4 yards a carry. Still, some skeptics said Allen wasn't in the class of the tailbacks of the past, that his blockers got him his yards. Allen heard the critics and he determined to quiet them.

Throughout spring practice he worked with John Jackson, the running back coach, looking at hours of film, working constantly on improving his vision and balance.

"We try to get our backs to run with their eyes," Jackson said. "We tell them to see where their blockers are, to see the tacklers. Marcus had a tendency as a junior to try to run over people. This year, he's been avoiding them more, slipping more tackles. That's why he's better."

The pros think he is great. Bobby Beathard, the Redskins' general manager, watched Allen on film recently. "Just a great back," Beathard said. "Everything you would want. Speed, size, good hands. Definitely the kind who might be the No. 1 pick in the draft. He reminds me a lot of George Rogers."

The difference, according to Robinson, may be Allen's versatility. He is almost as good a receiver as he is a runner. "I'm not sure he will be the No. 1 pick," Robinson said. "Look at him, he's not huge (6 feet 2, 202 pounds), not a dominant kind of back like an Earl Campbell or a Jim Brown.

"But he can do so many things. He blocks well, runs well, catches well. He would be great in a diversified offense. He might rush for more than 1,000 yards and catch 70 or 80 passes, too."

Allen has glided through this Heisman campaign. Southern Cal's sports publicity people say working with him has been a delight after their stormy year with White, who often balked at interviews or failed to show up for appointments. Allen almost always cooperates.

Unlike many star football players, Allen will graduate in four years,

"I've tried to keep the Heisman in the back of my mind and not think about it much," he said. "If you start thinking about it, it adds to the pressure and maybe you don't run as well or you start to make mistakes. The next thing you know, you don't have to worry about it anymore. I just go out and run and let what happens happen.

"I've been swamped a lot. But I enjoy most of it. I guess some guys don't like this kind of thing, but I do.

"At the beginning of the year I sat down with Coach Jackson and we set up some goals for me. I keep them private, though."

Did he expect to reach those goals?

"Yeah," he said. "I think I may make it."