The fifth year of "Playing Football" begins this weekend and I have but one regret: Why didn't the rules committee let the game alone? It was perfect the way it was - at least for me. So why liberalize the blocking rule to help the offensive linemen and restrict the bumping in the bump-and-run for the secondaries?

Dominant defenses have been central to the success of this column each season since 1974. That is what I look for in the unending battle against the point spread - defenses that can help generate offense.

The rules changes this year will make it more difficult for defenses to dominate. More points are going to be scored by everyone because the NFL office wants to please the fans. But Pete Rozelle certainly did not check things out with me.

The record in this space over four years is 140 winers, 96 losers, for 59 percent - a net mythical profit of $27,514 on an average of $350 per game. Last year was the best, at 34-15, for 69 percent. Each season has been a winning one, but then again George Allen never had a losing season and look what happened to him.

So much for puffery.

Nothing that happened in the past guarantees continued success, except I think the approach here is sound. I will continue to concentrate on the stronger teams. They are the most dependable and they are the ones to be seen most frequently on national TV.

The Giants, Tampa Bay, Green Bay, Kansas City, the Jets, New Orleans, Buffalo and Seattle do not merit serious consideration at this point. Detroit and Philadelphia are marginal. St. Louis and Chicago soon may be.

Caution and restraint during the early weeks are an integral part of the successful pattern. Do not become involved too heavily with what you don't know, as answers regarding many teams will not be available for perhaps a month. Relax, look and listen for a while. The season has been stretched two weeks longer. There is time.

I like Dallas, Los Angeles, Minnesota, New England, Oakland and Pittsburgh to capture the divisional titles, which is akin to touting baseball, hot dogs, apple pie and Chevrolet.

The Cowboys can only improve, what with Randy White settled in alongside Harvey Martin and Tony Dorsett ready to contribute from the start of this season. Washington might finish second in the NFC East and earn one of the conference's two wild-card slots. Much depends on Joe Theismann. But Allen is gone, and he was gorgeous when it came to devising defenses.

Los Angeles is still the best in the NFC West, although Atlanta's defense is superb and San Francisco could develop into a very respectable team by midseason.

Minnesota is the most improved squad in the NFC Central, where Chicago threatens to go downhill faster than Detroit can climb.

New England was the AFC East pick even before Bob Griese and Bert Jones were injured. The Patriots have great depth, a quality that is more important than ever this season. They also have an excellent, although relatively unknown, backup quarterback to Steve Grogan in Tom Owen.

Houston will press Pittsburgh for the AFC Central title, with Cincinnati and Cleveland good enough to win if only they were in another division. Oakland is a better team than Denver in the AFC West. Then again, the Raiders were the better team last year, only to finish second.

For starters, I recommend Cleveland giving four points at home against San Francisco. The 49ers' offensive line is open to question and the new coach, Pete McCulley, is banking on second-year quarterback Steve DeBerg to achieve what Jim Plunkett couldn't. O.J. Simpson may be a week away from prime time.

San Francisco's strength is its defensive line, anchored by Cedrick llardman and Cleveland Elam. Neutralize these two and you are in business. Cleveland should be able to hold its own up front on offense while dominating on defense. The Browns were 5-2 last year until quarterback Brian Sipe was injured. They will be a good team so long as Sipe, a Billy Kilmer type, stays healthy.

I will risk a mythical $500 on Cleveland.

In other games, Tampa Bay is favored by one point over the Giants, Detroit is nine over Green Bay, Houston 3 1/2 over Atlanta, Cincinnati 8 1/2 over Kansas City, Los Angeles 6 1/2 over Philadelphia, Miami four over the Jets, Minnesota seven over New Orleans, Oakland four over Denver, Pittsburg 11 1/2 over Buffalo, Chicago 3 1/2 over St. Louis, San Diego six over Seattle and New England nine over Washington.

Dallas opened 11 over Baltimore, presuming Jones would not play. If Jones plays, it should be 7 or 7 1/2.