Only seven teams are undefeated after two weeks of play in the National Football League. If form holds Sunday, that number will be chopped to three -- Pittsburgh, Philadelphia and Detroit. So tell me, does this exceptional balance exist because there is so much quality throughout the league, or so little?

I believe it is because there are more good players than ever, because the 1978 rules changes legalizing offensive holding have turned the game into a sandlot syndrome, and because the "parity" prescribed for the schedule makers penalizes the stronger squads.

No matter. Pete Rozelle and the fans are happy, and fan interest is what counts, through the turnstiles and in the television ratings.

The Las Vegas line indicates that Buffalo, San Diego, San Francisco and Tampa Bay are about to lose for the first time in 1980. New Orleans, although 0-2, is favored by one point at home against the Bills. The New York Jets, also 0-2, are four-point favorites over the 49ers. Dallas rules a seven-point pick as the host to the Bucs, and Denver is favored by two points at home to San Diego.

The three other unbeaten teams are solid choices: Pittsburgh by seven at Cincinnati, Detroit by 6 1/2 at home against St. Louis, and Philadelphia by 10 Monday night at home against the New York Giants.

As a rule, giving 10 points doesn't interest me. But the Eagles have been so impressive in devouring Denver and Minnesota that a mythical $500 risk is in order. Philadelphia's offensive line is providing blocking for Wilbert Montgomery and protection for Ron Jaworski. The defensive front and linebackers have hidden any deficiencies that may exist in the secondary.

The Giants do not figure to create many problems for the Eagle defense even though they scored 41 points in beating St. Louis and 21 in losing narrowly to Washington. New York will not be able to run on Philadelphia, which means Phil Simms will have to pass early and often. The Eagles will pressure him. Philadelphia has a solid advantage on both lines of scrimmage.

Jaworski, accordingly, should have time to throw into the Giants' weak secondary, while Montgomery enjoys another good effort running the ball. I doubt that the Eagles can improve on their first two outings during the remainder of the season. But while they are healthy, and confident, at the key positions, they are going to be difficult to handle.

Denver also attracts a mythical $500 play. This is a team that has lacked only one ingredient, a quarterback. Matt Robinson, acquired from the Jets, may fill that requirement. Not that Robinson is an exceptional passer. He's not. But he is mobile enough, unlike Craig Morton, to put some life into the Bronco offense, which in turn, should give the crack defensive unit new hope of winning a Super Bowl.

San Diego has the best passing game in the NFL. Denver counters with quickness at linebacker and in the secondary, however, to give Dan Fouts trouble.

Baltimore, getting seven points at Houston, is a $250 pick, as is Dallas, giving seven against Tampa Bay. Bert Jones once again is the league's premier quarterback. Anytime you can get Jones and a touchdown it's worth considering. Dallas gets the nod because the Cowboys should shut down Tampa Bay on the ground, forcing Doug Williams to throw more than Coach John McKay wants.

Three other contests are worth a little more nibbling of $100 each. I'll go with Detroit and Billy Sims in the Lions' home opener, Los Angeles to start getting untracked against Green Bay, and Seattle against unpredictable New England. The Rams are favored by 14, the Seahawks by 2.

In other games, Las Vegas lists Cleveland four over Kansas City, Atlanta three over Miami, Chicago six over Minnesota and Oakland 3 1/2 over Washington. Keep in mind the fact that home teams are 9-19 against the point spread after the first two weeks.

Forced to make a selection on Washington-Oakland, I would string along with the Raiders. They are 2-0 against the spread while the Skins are 0-2. The difference Sunday might well be the injuries in Washington's offensive line. When the two starting tackles and the starting tight end are injured, the entire team has to be hurting. (TABLE) Last Week(COLUMN)Season Total $110(COLUMN)270(END TABLE)

Last week: Philadelphia, giving 3 1/2, defeated Minnesota, 42-7, plus $250; San Francisco, giving 3 1/2, defeated St. Louis in overtime, 24-21, minus $110; Miami, giving 6 1/2, defeated Cincinnati, 17-16, minus $110. Net for week, plus $30. Net for season, minus $270.

Season record: 2-3.