Last weekend provided "Playing Football" with a refreshing experience in terms of the 1978 season.

I won.

An imaginary total of $355, to be exact, and if that is not exactly the bigest haul since the great Northfield, Minn, raid, well, it beats losing. The season's total is minus $2,020, which is not to be confused with a loss of 20-20 vision.

Still, the results of the last seven games are encouraging, showing a comeback of $1,105 from the early miseries. More important, the last two prime picks have been on target - Washington beating the plus-four point spread and Dallas, 9-5, and San Deigo charging past Denver as a 1 1/2 point underdog 23-0.

The ability to spot a defense primed for an excellent effort has been the essence of the approach in this column the last four years. Washington and San Diego fell into the pattern. That is encouraging. But before preparing to take off for the moon it is important to remember that the rules changes this season have altered the standard method for evaluating defenses.

For many years the most successful of the NFL's front four were able to conceal the weaknesses of linebackers and secondaries on pass defense. If the passer was sacked, or had to release the ball under pressure before his receive had made the cut, the secondaries were in heaven.

Now, suddenly, even the strongest of the front fours or front threes are being neutralized by the newly legalized clutch-and-grab tactics permitted by the offensive linemen. Offensive lines have adjusted to the stunts and loops defenses employed to advantage for several years. There is not one team in the league able to get to the passer on a regular basis without shooting linebackers and or safeties from the four-three or three-four.

Quickness is increasingly more important than strength in judging a defensive line's pass ruch potential.

This change, coupled with the receivers' having less to fear from "chucks" and, accordingly, more time to get deep, has turned around some of the thinking about defensive priorities, at least so far as "Plying Football" is concerned. The prime consideration now centers on secondaries, and Washington's is a classic example.

Here is a secondary that never did enjoy, in recent seasons, much help from a pass rush. For the Redskins' pass defenders, little has changed from the 1977 or 1976 seasons, although Lemar Parrish on the corner has been a valuable addition and Coy Bacon beefs up the pass rush. Tr for add three.

What has happened is that the secondaries on all the outstanding squads now are being forced to work under the same handicap that confronted the Washington secondary in recent years. And many of these heretofore highly regarded secondaries have not been equal to the task. Several have been exposed for what they are, and were - secondaries that are not nearly as capable as their pre-1978 reputation.

The only factor that has been as strong as this consideration in recent weeks is the home field advantage. Home teams were 11-3 each of the last two weeks. The outlook for the majority of the visiting teams beating the spread this weekend also is bleak.

I am going to go with Philadelphia, getting 2 1/2 points against Washington, strictly because of the home field atmosphere. The risk is a mythical $250, giving four at home against Seattle; San Diego, $250, giving four at home against Miami; Houston, $100, giving nine at home against Buffalo, and Los Angeles, $100 giving four a Minnesota.

The Broncos should be able to follow in the footsteps of Washington and San Diego the last two week shutting down Walter Payton on the ground and forcing Bob Avellini to try to get lucky up top. If Craig Mortion wasn't throwing so terribly, and Weese hadn't been injured, I would have moved in much more solidly with Denver.

The Las Vegas line finds Dellas favored by 14 at St. Louis, Atlanta six over Detroit, Oakland 13 over Kansas City, New England eight over Cincinnati, San Francisco, four over New Orleans, Baltimore seven over the Jets if Bert Jones plays, Pittsburgh four over Cleveland and the Gaints four over Tampa Bay.