The scratch and dent sale that is the 1981 National Football League season heads down the homestretch with no team still under warranty. Every club has proved vulnerable at one time or another, often embarrassingly so.
Take the three winningest teams on the lot, the Dallas Cowboys, Philadelphia Eagles, and San Francisco 49ers. Generally, they've looked strong in compiling 7-2 records, but how do you explain Dallas getting blitzed by the 49ers 45-14 or Philadelphia losing to Minnesota 35-23?
So before anyone starts checking into the playoffs, seven more weeks will be spent kicking tires and generally finding out which teams are true high-mileage performers.
''We've done OK the first half, but the second half of the season is the difference,'' said 49er Coach Bill Walsh. ''We don't really know where it will take us.''
Possibly to a division championship or better, judging from last Sunday's 17- 14 victory over Pittsburgh, which Walsh called ''our biggest physical test so far, especially playing away from home.'' San Francisco appears to be following in the cleat marks of other NFL prospectors to strike it rich (Denver in 1977, Tampa Bay in 1979, and Buffalo and Atlanta last year).
The 49ers are now two games ahead of Atlanta and Los Angeles in the NFC West and give every indication of being more than a flash in the pan. Their quarterback, former Notre Dame star Joe Montana, comes armed with the league's top statistics, the passing game is well conceived, and the defense rejuvenated. For San Francisco to win its first NFL title, newly acquired defensive end Fred Dean would have to continue playing like the league's Most Valuable Player, which he just might be.
Traded by San Diego for future draft choices, Fred has put ''sack'' back in the 49er defensive vocabulary. John Jefferson, meanwhile, has also exited San Diego after failing to renegotiate his contract and now joins with James Lofton to give Green Bay perhaps the game's best receiving tandem.
If the Chargers, co-leaders of the American Conference's Western Division along with Kansas City and Denver, have looked unsure of themselves, the loss of these two players is probably the reason. As San Diego quarterback Dan Fouts assessed the situation, letting Jefferson get away was akin to trading Willie Mays in his prime.
On the whole, Dallas and Philadelphia may be the most even-keeled of the NFL's 28 teams. They've unlocked the winning formula and seldom deviate from it. Success breeds success as they say.
Last Sunday these rivals squared off in their first head-to-head meeting since last season's NFC championship game, won by Philadelphia. The contest was pretty much a defensive struggle, the Cowboys winning 17-14 to move into a first-place tie with the Eagles.
Eagle placekicker Tony Franklin, who had failed only one other time this season inside the 40 yard-line, did so from 34 yards out in the game's last two minutes. Making matters worse for the largest crowd (72,111) in Veterans Stadium history, Philadelphia let Dallas off the hook after holding a 14-3 lead late in the third quarter, injured Eagle quarterback Ron Jaworski couldn't finish the game, and the rematch between the two teams is scheduled Dec. 13 in Dallas.
While the Cowboys and Eagles are busy giving the NFC a good name (something it hasn't had for a while), residents of the NFC Central are doing their usual impersonation of flimflam artists. The division leaders are Minnesota and Tampa Bay with 5-4 records, and only the Vikings, with Tommy Kramer operating a pass-oriented ''sandlot'' offense, has dazzled anybody.
It's beginning to look like the Pack may never come back under Green Bay Coach Bart Starr, whose job certainly must be in serious jeopardy. But anyone who thinks the 3-6 Packers are in sorry shape only have to cast their eyes upon 2-7 Chicago Bears, who appear totally confused. In what can only be considered a desperate move, owner George Halas brought in former coach Jim Dooley (20-36 at the controls) as an offensive consultant.
Ironically, the division that most resembles the NFC Central is its American counterpart, once thought to be the NFL's strongest. But times, teams, and personnel change, and now the AFC Central is less potent, though no less exciting. Cincinnati leads the way with a 6-3 record, followed by Pittsburgh (5 -4), then Cleveland and Houston, both 4-5. A sign of the times is Cincinnati's three-game winning streak over the Steelers, who more and more look like an ordinary team. Cleveland hasn't been giving QB Brian Sipe the protection he needs, and Houston can't quite figure whether overworked runner Earl Campbell should be the be-all and end-all of the offense.
Over in the AFC East, fans are bracing themselves for what could be a real rip-roaring finish. Coach Don Shula continues to work his magic on the 6-2-1 Miami Dolphins, who, by dint of a tie, own a half-game lead over the Buffalo Bills (6-3).
Miami had a chance to open up a little space on the Bills, but lost a 28-27 heartbreaker to Dallas two weeks ago, allowing the Cowboys to erase a 13-point deficit in the final five minutes. ''It could have been one of our great wins, and instead it turns out to be a bitter defeat,'' said Shula.
The Bills, who seemingly had lost some of their defensive intensity, found it the last two weeks, when they recorded 13 quarterback sacks. ''Now we're saying , 'Hey, we've got to get down to business,'' explained cornerback Mario Clark of the aroused play. At 4-4-1 the New York Jets aren't out of it either, though they have been plagued by inconsistency.