It is Sunday, the last day of the NFL regular season and Tampa Bay, for all its problems, manages to squeak past Kansas City, 13-10, thereby capturing the NFC's Central Division.

An hour later, in Chicago, the Bears walk off the field with a 24-17 success over St. Louis. Chicago still has a chance to gain the second of the NFC's two wild-card berths, but the "net points in all games" shows the Bears 26 behind the Washington Redskins. The spread between the two teams at the start of the day was 33.

Washington knows the final Chicago score as the Redskins go to the locker room for halftime in Dallas, trailing the Cowboys, 14-7. Their situation does not improve during the second half. Roger Staubach passes to Drew Pearson and it's 21-7 midway in the third quarter. Early in the final period Tony Dorsett busts loose for 60 yards, making the score 28-7.

Normally, with several players hurting, Dallas would rest its wounded over the final minutes. But no. Randy White stays in the game. So does Dorsett. And Robert Newhouse.

The Cowboys remember. They remember the field goal Mark Moseley kicked against them in the final minutes in Washington earlier in the year.

Now thre are less than two minutes to play. Dallas takes over on its own 20. The redskins are out of time outs. The Cowboys have three. They use all three in driving to the Redskin 10-yard line. Staubach goes to the sidelines to confer with Coach Tom Landry. They decide not to kick the field goal because a 24-point loss (31-7) would keep Washington in the playoff picture.

Staubach calls for a triple reverse with a pitch back on the tail end going to the quarterback, who throws to Tony Hill in the far corner of the end zone. Touchdown! 35-7. Chicago edges the Skins by two points in the all-important "net points in all games" category, immediately giving a new dimension to the term point spread.

None of this could happen, of course. No team could be that mean, that nasty, that Machiavellian, that it would go so far as to try to bury a team it had beaten, could they?

I'm just daydreaming about the possibilities of such a situation. But I will invest $250 on the Cowboys giving nine points in the belief that hate is a great motivator. This might be one time that Dallas won't sit on a 10-point lead.

The big pick for the week and the season, however, is San Diego giving 6 1/2 Monday night at home against Denever, risking a mythical $3,000. This is the maximum amount "Playing Football" invests on any one game.

I hesitate to do it only because it looks like a get-out selection, a desperate attempt to get even for the season and to show a profit before the playoffs. But that is not true. I have waited for the return match since Oct. 7 when, favored by one point, the Chargers lost in Dever, 7-0. The Bronco touchdown was set up by the return of a fumble after Dan Fouts had completed a pass.

If you believe in offensive and defensive line match-ups -- and I happen to live or die by them -- San Diego should win handily. Fouts will have all the time in the world to throw. He enjoys the best pass protection in the league, and Denver's defense, while excellent against the run, does not stop a high-powered passing attack.

Conversely, Denver's Craig Morton is going to be subjected to extreme pressure from San Diego's pass rush. Morton is the classic example of an aging quarterback who desperately needs time to set up and spot his receivers. He cannot stand the threat of being punished. The Chargrs will get to him.

There is no such thing as a "lock" or a sure thing in gambling. I have risked $3,000 before and lost. It could happen again, but the percentages are overwhelming in the Chargers' favor. They need their victory to beat Denver for the AFC West and assure themselves the home field through the playoffs.

I will also risk $500 this week on Oakland, giving 7 1/2 at home against Seattle. The Raiders continue to improve while the Seahawks have lost their splendid receiver, Steve Largent. Oakland should make the playoffs if it winds up 10-6.

Finally, the Giants are worth $250 at home against Baltimore, giving 6 1/2. The Colts are a sad story in 1979 while New York is happily looking ahead to 1980.

In other games, Las Vegas lists Miami 6 over the New York Jets and Detroit 3 1/2 over Green Bay on Saturday; Pittsburgh 13 over Buffalo, Cincinnati 3 over Cleveland, Tampa Bay 3 over Kansas City, New England 6 1/2 over Minnesota, Atlanta 4 over San Francisco, Chicago 4 1/2 over St. Louis, Los Angeles 5 over New Orleans and Houston 6 over Philadelphia.