Once upon a time, like last year or the year before, it was an easy question: Best offense in the NFL? Come on, even a non-fan was able to answer that quicker than you could say, “Sage Rosenfels fumbles again!”

It was the Patriots. Or the Colts.

The Bradys or the Mannings, depending on the week, month, year, etc.

Now? Hmm. This is going to require some thought, some analysis.

We’ve seen a lot of great offense over the first five weeks of the season. Individually, there was Brett Favre’s six-touchdown pass game, Ronnie Brown’s four-touchdown masterpiece, Brandon Marshall’s 18-reception domination and Michael Turner’s 220-yard rushing day.

But the best offensive team. We studied the statistics, talked to an objective scout and broke down lots of game tape (OK, maybe we just caught some highlights). The candidates were narrowed to the Broncos, Cowboys and Giants, and the winner is …

The Cowboys.

They’re ranked No. 2 in scoring average and No. 3 in total offense, with Tony Romo the fourth-rated passer and Jason Witten the second-leading receiver in the league. But our grading system went beyond the obvious. We dug a little deeper and based it on four categories:

Balance
The Cowboys can beat you with the run or the pass. They can line up and play smashmouth, attacking with the thunder and lightning backfield of Marion Barber and Felix Jones, the rookie that takes your breath away. If you want to key on the run and put eight men in the box, the Cowboys will adjust and simply throw the ball all over the yard to Witten, Terrell Owens and Patrick Crayton.

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No other team has that kind of balance. The Giants come close, real close. Teams like the Broncos and Saints can throw all day, but they don’t run the ball well enough to call themselves true two-dimensional offenses.

Explosiveness
This is what offensive football is all about, isn’t it? It’s about big plays. Once again, the Cowboys get the nod here. They’ve produced 25 plays of at least 20 yards (including six in the 40-plus category), which is pretty darn impressive. For them, it averages to one “explosion” play every 10 snaps, a remarkable ability to tilt the field.

That places an extraordinary burden on the defense. Opponents must stay back, respecting the Cowboys’ big-play potential. That, in turn, creates seams in the underneath and intermediate passing lanes. This is where Witten is at his best, working the middle and tormenting Cover-2 zones. Clog the middle, and it gives T.O. room on the perimeter. Romo’s ability to improvise, sliding in the pocket to avoid the pass rush, buys time for the receivers to get open downfield.

It’s a lethal cocktail.

Consistency
Let’s face it, anybody can get hot on any given week — heck, even the Jets scored 56 points in a game — but the trick is to do it over and over, home and away. This, too, belongs to the Cowboys, who have yet to score less than 24 points in a game. And they’ve done it against a fairly difficult schedule, having faced two top 10-scoring defenses — the Eagles and Browns.

The undefeated Giants are a wonderful team, and they’ll get better as Eli Manning continues to mature, but they haven’t faced any top-10 defenses. Truth is, they’ve played two of the worst, the Seahawks and Rams. The Broncos? If they see anymore Swiss cheese, they’ll start yodeling.

Scheme/play calling

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Although he hasn’t called the plays in several years, Broncos coach Mike Shanahan still ranks as one of the league's top offensive minds. Just give him a competent triggerman, which he has in Jay Cutler, and Shanahan can score points on anybody, regardless of the backs and receivers. A head coach once told me that Shanahan is the best in the league at identifying an opponents’ weakness and hammering away at it, even if it makes him stray from his own tendencies.

Cowboys offensive coordinator Jason Garrett isn’t on Shanahan’s level, not yet, but he has a firm grasp of personnel and a good feel for the flow of the game. He can kill a defense with draw plays, especially now that he has a speed back in Jones, and plays to Romo’s strengths.

Of course, the fans never are satisfied in Dallas, where last week’s too-close-for-comfort win over the lowly Bengals has fueled great concern. Yes, Romo has thrown an interception in eight straight games. Yes, he has committed seven turnovers in five games. It could be a problem, especially in January against an efficient, mentally tough team such as the Giants, but they’re winning right now.

For our money, Big D owns the Biggest O.