Five years ago, Joe Montana was the football equivalent of a baseball relief pitcher.

His bailing out of Notre Dame with game-winning performances has become part of the Irish legend. Yet, until midway through his junior year, he couldn't beat out someone named Rick Slager.

Three years ago, Montana was a rookie professional with an average throwing arm that had kept him in the draft pool until the third round.

His 49er coach, Bill Walsh, noticed him only after Montana threw passes during a workout to UCLA running back James Owens. Owens became San Francisco's No. 1 pick. Montana was considered a good bet only to survive the final roster cut.

This year, Montana, now 25 and a veteran of 18 professional starts, has become a celebrity. An obscure player in preseason, now he can't walk past a newsstand without seeing his picture on the cover of some prominent magazine previewing the Super Bowl. The media is scrambling to learn the most minute details of his life. His parents are being interviewed, his former coaches are recalling their predictions about his future, Walsh is saying over and over how he always knew Montana was destined for greatness. He also says Montana will be the best quarterback in the NFL within three years.

Still, even Montana can't explain how so many people have misjudged his abilities for so long, why he couldn't convince Dan Devine, his college coach, that he should be a starter, why he couldn't impress pro scouts enough to be drafted higher.

"I always thought I could do the job when given the chance," he said today. "I don't know why things didn't work out differently before."

Possibly it's because Montana, out of uniform, doesn't fit the image of a star quarterback. His idol is Joe Namath, but they are alike in only one way: Both come from Pennsylvania.

Namath is outgoing, glib, a natural public figure. Montana still has a little-boy shyness about him that is revealed in a self-conscious laugh.

Namath was a star, at home in New York City or Beverly Hills. Montana prefers the isolation of the hills above San Francisco.

Namath told people he would win games, then made the prediction come true. Montana keeps pulling out impossible victories, but afterward can't explain how he did it.

But on the field, his personality changes.

"In the huddle," guard Randy Cross said, "there is something about Joe that tells you he will do the job. He takes charge. You believe in him. Without that, a quarterback really hasn't got a chance."

Montana will chew out teammates during games. He will become so emotional during tense moments that he has to prevent himself from losing control. He will accept moments of pressure with boldness because "I'm not afraid of them, even though I don't look for them. But I won't back away."

Says his wife Cassie, "The Joe Montana I see on the field sometimes is not the Joe Montana I know at home. We laugh about that sometimes. He changes so much."

A Notre Dame fan once wrote a "Ballad of Joe Montana" about the quarterback's penchant for the dramatic. Namath had it. Billy Kilmer had it. Bobby Layne had it. It can't be taught, not even by Walsh, the master tactician and molder of quarterbacks. And scouting tests can't measure it.

"What makes one man play his best under pressure and another fall apart? I don't know," Walsh said. "But to win, your quarterback has to be able to face up to challenges. There is something inside Joe that makes him special."

Montana knew he wanted to be a quarterback almost from the first day he began playing football in Monongahela, Pa. He has spent much of his youth perfecting the required skills, even though his thin body and his weak arm didn't always cooperate.

He also had the good fortune to be in the right places at the right times. Where better to learn to cope with pressure than at Notre Dame? Who better to learn the position from than Walsh, who already had produced two NCAA passing champions and two NFL passing leaders?

"Bill has given me an understanding of the game that I never had before," Montana said. "His offense is so detailed and his mind is so active. He is never content with what we have. He wants to always add and refine things. It's made me work harder. I've had to study long and hard just to keep up."

Whether Montana would have won the NFC passing title this year (3,565 yards, 19 touchdowns, 64 percent completions) without three years of Walsh's tutelage seems unlikely. Walsh had a three-year plan in mind for Montana, and made the decision to trade away former starter Steve DeBerg and hand the job to Montana.

San Francisco's offense is ideal for Montana's strengths. He is not asked to throw long often, concentrating instead on short and medium passes that do not need a strong arm. He is given a safety valve receiver on every play so he will not have to force passes into coverage. And he is encouraged to scramble to set up ad-lib situations that he can exploit with his quick thinking and ability to pick out open receivers on the run.

"The only guy in the league as dangerous out of the pocket as Joe is Brian Sipe," said Hank Bullough, Cincinnati's defensive coordinator. "No one writes about how they have planned runs for Montana. His running ability gives them something most teams don't have. He creates situations on the move. How do you defense something that doesn't happen until the moment he leaves the pocket?"

The 49ers pay Montana about $100,000 a year, a figure that Walsh, the team's general manager, admits will skyrocket if Montana lives up to his coach's expectations.

But Montana, unlike the Rams' Vince Ferragamo two years ago, is not dreaming this week about lucrative contracts. He is too busy coping with Walsh's demanding practices and the avalanche of interviews. He is rare among modern athletes in that he hardly ever turns down a request, usually staying until the last question is asked.

Today, Montana was quizzed repeatedly about his admiration of Namath, who became a legend by winning Super Bowl III for the New York Jets.

Montana smiled uneasily.

"Do I want to emulate Joe's life style? Well, I don't know about that. But I sure hope I'm like him in one way," Montana said, his eyes glaring briefly. "I want to come out on top in a Super Bowl, too. This Super Bowl.