CARLISLE, PA. -- So many tiny, seemingly unrelated events push a young athlete toward a particular path. Let's say a former high school quarterback with absolutely no desire to play college football had not gotten one of the all-time lousy grades in biology. He might be Dr. Richard Alvin Petitbon, New Orleans dentist, comfortable in middle age now instead of in the process of a serious career decision.

Hard as it might be for anyone in the National Football League to imagine Richie Petitbon tightening teeth for a living instead of finding ways to occasionally loosen them, that was a thought 35-plus years ago.

What helped change Petitbon's mind was a course taught by a blunt professor whose name and face still remain fairly vivid to the Redskins assistant head coach/defense. On one of the tests, Petitbon might have broken new ground for failure with that grade well below rock bottom, a staggeringly-awful score of minus-45.

"I did rally for a D," he said.

Intent on avoiding what has provided his living through parts of five decades, Petitbon had enrolled at a non-football college, Loyola of New Orleans. That was well before his stomach began arriving at places before the rest of his body, when he was a runner worthy of a track scholarship.

"I ran 9.8" for 100 yards, he said, "which was great in high school but wouldn't win too many meets in college. So they switched me to the 440. After a few of those, I figured football couldn't be as tough. So I walked across the street, to Tulane, and asked if that football scholarship was still available."

"It was -- and that's how all this started. The quarter-mile was responsible."A Step Up in Time

Any player who survives 14 years as a pro, as Petitbon did with the Bears, the Rams and the early George Allen Redskins, has an abiding affection for football; after another 16 years as an assistant, most of them at the coordinator level for the Redskins, it is time to toss his clipboard toward the NFL head-coaching ring.

Not into the ring exactly, because Petitbon insists, "To have a head-coaching job is not that important; to have a good head-coaching job is very important."

By a good head-coaching job, Petitbon mostly means one where the ownership is stable and upper-management enlightened. Such as the Redskins, where Jack Kent Cooke places enormous pressure on Joe Gibbs and his staff to win but also provides most of the requisite tools.

Petitbon only once has gone after such a job, the one in New Orleans that Jim Mora got five years ago. He may become less selective, for a couple of sound reasons.

In a business where insecurity is a given, Petitbon in 16 years has been a coach in only two cities: Houston, from 1974 to 1977, and Washington. His children not only experienced a measure of high school stability but also are out of college.

Also, Petitbon is 52. If that hardly makes him close to petrification, he is two years older than Gibbs and two years older than the most recent Redskins aide to leave for a command of his own, Joe Bugel. Very rarely, he knows, does the job pursue the man. With fewer ties to Washington, why leave a dream even partially incomplete?

"He's one people are looking at and have talked about," said Gibbs. "But he's also smart enough not to jump at just anything."

What advice might Gibbs have?

"For each guy it's different," he said. "Some guys I'd say: 'Hey, take this. No matter what. No matter where it is.' You can tell it may be their only chance.

"For other people, it's knowing where they are -- and knowing what that other side's like. It's a shock for some guys. I'd be willing to say right now, if you talked to Buges {in Phoenix with the Cardinals} there's a lot of negatives."

"Richie's strength would be game day," said General Manager Charley Casserly. "He has a sense of what it takes to win in this league. He knows how important it is to hire a good staff. Some head coaches are organizers, some are promoters, some are tacticians.

"Richie would be a tactician. Offensively and defensively, he knows right from wrong. He would not get outcoached."

Petitbon has noticed contemporaries such as Mike Ditka, Jack Pardee, Maxie Baughan, Dan Reeves and Forrest Gregg taking their chance. At least one, Pardee, scurried back into football, in Houston, a few years after being fired by Cooke following the 1980 season.

"I really believe football is the best game in the world," Petitbon said. "It's more like life than life itself. And going from playing to coaching is like an actor who learns his trade and then switches to directing.

"The reason athletes have trouble adjusting to life after football is that it's very difficult to experience the highs you get from winning. And the great thing about losing is that next week you get to roll the dice again."

More than it seems on the surface, football attracts men inclined toward gambling. Every play, after all, is a guess.

"That's also what doctors do half the time: guess," Petitbon countered. "You have to know what the odds are. You take your shots now and then. I think the good ones guess right most of the time. That's what it's all about.

"There is no such thing as a good call or a bad call. You have to look at the whole game, or the whole season. On any given play, you can be right or wrong. Lots of times, you're right when you're wrong. You'll see a receiver wide open, but we've gotten a sack."

To those who say he is too wedded to the traditional 4-3 defense, Petitbon in his casual way might say: "Hey, babe, I helped invent the 3-4."

That was with the Oilers of Bum Phillips in the mid-'70s, when Petitbon was coaching the defensive backs.

"Miami had been using the 3-4 a bit," Petitbon said. "We were the first to use it exclusively. And were very successful. If we had Lawrence Taylor, we'd be in the 3-4 right now."

Some would argue the Redskins have a Taylor-like player in Wilber Marshall.

Petitbon: "He's very solid, one of the best in the league. But Lawrence Taylor might be the best defensive football player in the history of the game. He's the most dominating player I've ever seen."Witness to Game's Evolution

From his rookie season as a safety with the Bears in 1959, Petitbon has seen pro football evolve from being a part-time job to a career that can leave a player set for life after a half-dozen or so seasons. He sold life insurance during many an offseason.

Two coaches for whom Petitbon played, George Halas and Allen, frequently tightroped ethics. Because it was mandatory, opponents always got films of recent games from Bears, Rams and Redskins. However, those films might not have been put on a plane until two days after they could have been. And new formations almost certainly were snipped out. Just to make sure the other guys weren't also doing selective editing, Halas and Allen had spies.

"We'd practice against stuff {the opposition} never showed before," Petitbon said. "Sure enough, we'd see it during the game. It had to be coming from someplace, but it took me awhile to put it together. For the longest time, I just figured we had a smart coaching staff."

Smart is one of the overworked adjectives in football. A coach who guesses right twice in the same series is seen as smart; a coach who wins more than 10 games in a season is judged a genius. Petitbon early in his career played for a genuine innovator, Clark Shaughnessy.

"So many things people take for granted {now} he was doing in the '40s," Petitbon said. "He devised the T formation; he was the first to use three wide receivers. He walked out on us {as the Bears defensive coordinator} in 1962 and George Allen took over.

"One thing Shaughnessy always taught is something I still try to use every week: Always give the opponent something new. Never become predictable."

Predictably, Petitbon is close to furious at recent rule changes he insists "are legislating defense out of football. . . . Any team could save a lot of money by not buying shoulder pads for the offensive linemen. They don't need them" because new blocking rules allow for so much holding.

"Let us use our hands as much as offensive linemen use theirs. I'd also like to see us go back to being able to bump receivers all over the field -- and to be able to cut receivers at the line of scrimmage. Got to give those guys something to think about. Right now it's too easy for them."

With so many defensive linemen either going out of the Redskins' lineup with injuries or not coming into camp because of contract disputes, Petitbon jokes he might not switch to a 3-4 alignment but to a never-seen 2-5.

"But something good will come out of this," he said. "When you're at your lowest ebb, something good always comes up. And when things are going too good, generally something bad's going to happen. Like life. You've got to hang tough. Plug away."