The worst mistake anyone could make at the moment is to assume the imminent demise of the Dallas Cowboys, that having lost three of four games they are basted and ready to be carved by Houston Thanksgiving Day.

National Conference teams are both grateful and cautious about the Cowboys' drastic dip, at the time of the season they usually push the button marked "get serious" on their helmet computers and blow by everyone and into the playoffs.

Most NFC thinkers are silently waiting for enough friction to cause the sort of victory explosion for which Dallas is famous. Thomas Henderson might just be the spark. But it is possible to take an analytical, cold, unemotional, Cowboy-like view of the Cowboys and suggest some problems harmful both for their immediate and long-term future.

A reasonable person might wonder what could possibly trouble a young team that has been to the Super Bowl three of the last four years, beyond Randy White's foot and John Fitzgerald's knee injuries.

Those are more serious than outsiders might realize -- and they dramatize small but potentially serious errors that seem to have taken place the last four years. In truth, the best way to find several answers about the Cowboys is to ask one question:

What do Jim Jensen, Jim Eidson, Glenn Carano, Larry Bethea, Todd Christensen, Robert Shaw and Aaron Mitchell have in common? They are first - and second-round draft choices the four years who either have not played for the Cowboys or have not played well.

Of course, Tony Dorsett was a No. 1 in '77 -- and another exceptional player, Tony Hill, was a No. 3 that year. And Aaron Kyle and Tom Rafferty of the '76 draft also are regulars. But aren't the best judges of athletic meat on the hoof supposed to do better?

They are, but they haven't. Longtime NFL watchers realize that while the Cowboys' bottom-line performance for the last decade or so has been inspirational, how they got there has been strange. The harsh truth is that the Cowboys have botched as many high-round draft choices as anyone in the league.

Dennis Homan ('68), Tody Smith ('71), Bill Thomas ('72) and Charles Young ('74) are first-round Cowboy choices who played themselves into obscurity rather quickly. And in three of the first four years of their lives, Dallas imitated George Allen, of all despired people, and traded its first-round pick for veteran players.

Is this any way to build a dynasty?

Well, the Cowboys have been to the playoffs 12 of the last 13 years -- and the major reason has been thir immense success with low-round draftees and obscure free agents. Cowboy history is loaded with such men as Jethro Pugh, an 11th-round choice, and free agents such as Cornell Green and Cliff Harris.

The Cowboys live by the dominant-player theory. They believe in lassoing a half-dozen players capable of making All-Pro for years in a row and surrounding them with spirited, although perhaps almost marginal, talent.

A Bob Lilly makes players near him better, as do a Calivin Hill, a Randy White, a Tony Dorsett, a Roger Staubach and some others.

They acquire these players using the conventional system unconventionally.

What they do is trade and draft at the same time. Or more specifically, they trade to improve their draft position. They did it in '74, '75 and '77 and acquired the heart of their defense and Dorsett.

The Cowboys know that finishing as high as they do year after year gives them relatively poor position in the draft -- and that the difference between the first five players in the first round and the last five is far larger than even many insiders realize.

So Tex Schramm has used the Cowboys' reputation to fleece some poor teams into trading top first-round draft choices for overrated, although glamorous, players. For instance:

In 1974, Dallas traded the afore-mentioned Tody Smith and wide receiver Billy Parks to Houston for the first choice in the NFL draft, Too Tall Jones. The next year, Dallas traded the infamous Craig Morton to the Giants for the draft choice that became Randy White. Two years later, Dallas traded with Seattle and drafted Dorsett.

Now we know what boosted Dallas to preeminent position in the NFL the last 15 years, superior minds on the sideline and in the front office and an enormous amount of Clint Murchison's money to scour the land for players.

Why the possible decline?

At the moment, injuries and retirement have caused Dallas to approach the rest of the NFC and lose badly to the Steelers and Browns of the AFC. The line is the key to the defense -- and the left side vanished, or diminished badly, with the retirements of Pugh and Jones.

The Cowboys admitted as much recently when they traded for another cornerstone, John Dutton. They gave the Colts not the usual expendable Cowboy but Nos. 1 and 2 draft choices. Allen must be smiling; the rest of the league is snickering, privately whispering that Dutton simply will not justify the deal.

With White hobbling, the Cowboy defensive scheme for the run-oriented Oilers appears jumbled, if not chaotic. It seems certain, however, that if the Cowboys make the playoffs again, the offense will carry them.

"They've gone through the things most of us in the league go through from week to week," Redskin Coach Jack Pardee said. "From the games we've seen, other than the Rams game, they just haven't gone out and dominated like they did. They're had to come from behind a lot.

"What it boils down to is that they're not unlike all the teams in the league."

What's beyond this year, with their top draft choices already committed to Dutton and Staubach turning 38 in March?And what one league executive calls: "four lousy drafts in a row, with the exception of Dorsett and Hill."

The Cowboys have squirmed out of such seasonal predicaments before, although this one seems the toughest yet, even if White mends in a hurry. They also have righted their future at a time when much of the league was forecasting gloom, if not doom.

That was in 1975, after they finished 8-6 and missed the playoffs for the first time in nine years. At last, everyone said, the Cowboys are aging. They've been caught in a down cycle. They're vulnerable after all -- just like us.

Temporarily.

That year, Dallas needed a miracle draft -- and got one. A dozen rookies made the team and eight of them eventually became starters. In order, they were White, Henderson, Burton Lawless, Bob Breunig, Pat Donovan, Randy Hughes, Herbert Scott and Scott Laidlaw.

From mediocrity the year before, Dallas went to the Super Bowl. Some suggested it was Landry's finest season. He was more inventive than usual and the team was overflowing with what he believes it now lacks -- emotion.

The Cowboys have stayed higher longer than any recent NFL team. At the time the nation seems to have fallen for them, America's Team seems mortal. But if the rest of football is taking a hard look at the Cowboys, it is certain they are looking at themselves even harder.