What's going on in the National Football League?

A calculator was needed to total the points scored in last week's games: 606! That's approximately 100 over the 1978 average.

New England, which has an excellent offense, posted 56; Buffalo, which doesn't, had 51. Four teams scored in the mid-20s and lost.

So what's happened to the defense?

Answer: everyone's gambling.

Now, before anyone calls the cops, let's be quick to point out that the gambling is legal. It's merely the continuation of a trend that began last season when the rules were changed.

Offensive linemen now can do just about anything they want, short of strangling, to keep the pass rushers off the passer's back. Receivers have more time, and more freedom (from the chuck) to maneuver into the open. Quarterbacks, even the mediocre ones, have extra time in which to spot their secondary targets.

Defenses which, pre-1978, were able to get to the passer by conventional measures, without blitzing, are no longer able to do so.

It took many of the coaches a long time to realize that adjustments would have to be made. But by last year's playoffs, Chuck Noll was leading the charge into the changing world. The conservative Pittsburgh coach put All-Pro Jack Ham on a blitzin' binge. It paid off.

But there is a great risk, or gamble, inherent in trying to get to the passer with a linebacker or a safety. Some part of the defense becomes vulnerable or exposed. What works in Pittsburgh may be a disaster in New Orleans, because of the personnel involved.

Yet the defenses have little choice. They must gamble increasingly as this season progresses. Darn near any quarterback, given additional time to throw, will be success- ful. A fifth defensive back is no substitute for increased pressure.

There are a number of moderate quarterbacks now at work who can begin to look like John Unitas if they are free of the fear of footsteps. Denver's poor old Craig Morton is an excellent example. He will do anything to get rid of the ball -- even hand it over to the opposition -- to avoid getting crunched. Philly's Ron Jaworski is another who becomes very tentative when attacked.

The net result of this change in defensive tactics -- by that, I mean, more high-risk blitzing -- is that the game will continue to open up. When the blitz is successful it will, directly or indirectly, prompt more turnovers. When it fails, the offense is going to be able to strike more quickly and more dramatically.

Which is exactly what the NFL wants to see happen. The defenses had become too dominant, the game too "dull." Pete Rozelle is much happier with a 35-31 Super Bowl than he is with 14-7. Rozelle wanted more gambling . . . by the defenses, and that's exactly what the '78 rules changes have achieved.

As for the other kind of gambling, with mythical money, well, this week's card is no time to go overboard. Keep studying. Keep watching the tube and checking Monday morning's statistics. There is a long way to go.

What little action I plan this week has as much to do with the teams I don't like as with those I do. Detroit is in big trouble without Gary Danielson. So are the Giants with Joe Pisarcik. They make the New York Jets, giving 6 1/2 points, and the Washington Redskins, giving 5 Monday night, look a little attractive. The risk is minimal, $250 each.

I'll also string along with Green Bay, giving 2 1/2 at home to Tampa Bay, for $250, and throw in $100 on Pittsburgh giving 6 1/2 at St. Louis. The Steelers scare me. No team should look this good this early.

In other games, Cleveland is a 7 1/2-point favorite over Baltimore, Atlanta is 3 1/2 over Denver, Philadelphia 1 at New Orleans, New England 6 at Cincinnati, Houston 6 over Kansas City, Miami 7 over Minnesota, Seattle 3 over Oakland, Los Angeles 13 1/2 over San Francisco, San Diego 10 over Buffalo and Dallas 9 1/2 over Chicago.