Usually, playing on the road in a dome is dangerous because of deafening crowd noise and the home team's familiarity with the green concrete that stands in for a playing field.
For the Eagles, Sunday's game against the Minnesota Vikings at the Hubert H. Humphrey Metrodome is dangerous for another reason entirely. In the climate-controlled conditions of the dome, the temptation to throw the ball on every down may be too much for Andy Reid and offensive coordinator Marty Mornhinweg to resist.
We're not exactly talking about two guys with great willpower here, not when it comes to passing the ball. No wind, no cold, no precipitation of any kind? You may not see an Eagles handoff until the third quarter.
The irony is that the pass-crazy tendency dreaded by Eagles fans (and, I would argue, many Eagles players) might be perfect against the Vikings' defense. Minnesota finished the regular season ranked No. 1 in the NFL at stopping the run (based on yardage) and No. 18 at defending the pass.
Sometime this week, Reid and/or Mornhinweg will be asked about offensive balance and will respond that their approach is to do whatever they believe will work against a particular opponent.
"The first thing is, we try to do what it will take to win that particular football game," Mornhinweg said last week.
One of the fundamental tenets of the cult of the West Coast offense is that it can be tailored to attack the opponent's perceived vulnerabilities. It is also one of the fatal flaws of the West Coast philosophy, because it plays to the vanity of the coaches who embrace it.
It's easy (in their view) to have a specific approach and stick with it regardless of who is lined up across from you. It used to be said defenses knew that Vince Lombardi's Packers were running a sweep or Joe Gibbs' Washington teams would run the counter trey. That didn't mean they were able to stop either. The power of those trademark plays was in the execution, not the element of surprise.
The shape-shifting West Coast approach requires the offensive genius to take apart the opposing defensive scheme and personnel and identify weaknesses, then install a game plan with dozens of new plays that must be mastered during the week of practice. It is all about coaching, in other words. The players are interchangeable - indeed, there are personnel groups running on and off the field after every down.
The Eagles have won a lot of games doing things this way. So have other West Coast-based teams in the past. There is something to be said, however, for establishing a firm identity for your offense (and defense, for that matter) and sticking with it regardless of the opponent.
The New England dynasty of this decade changed year to year, according to personnel, but Bill Belichick's Patriots came at you their way - not yours. The Indianapolis Colts' offense, like that of the St. Louis Rams of the early 2000s, has been based on the assumption your defense can't match its talent level even when you know what's coming.
It is not a coincidence that the Eagles' best all-around performance of this season came at the Meadowlands on Dec. 7, when relentless wind forced them to run the ball much more against the Giants than they otherwise would have. The elements made the Eagles into a here-it-comes, try-to-stop-it offense, and the players embraced that.
Two weeks later, at Washington, it was back to outsmarting everyone. Reid and Mornhinweg threw and threw, supposedly because Washington kept a safety up to stop the run. By letting Washington defensive coordinator Greg Blache dictate their play-calling that easily, the Eagles blew a must-win game.
Reid took so much heat for that, he was actually asked if he wanted to gloat after coming back and crushing Dallas to earn a playoff berth. He declined, because he's not wired that way. But it's also true that any "I told you so" coming from the NovaCare Complex would be countered with one from observers who noticed the Eagles' play-calling was 50/50 run-to-pass in the first half against the Cowboys.
No one expects or wants Reid to go back to the 1960s and pound the ball on the ground. You have to throw to win in the NFL. You have to. But you also have to be able and willing to run in certain situations, in order to keep defenses honest, in order to burn time, in order to make play fakes effective.
When Reid and Mornhinweg embrace that, the Eagles' offense has been much more effective. When they don't - when they're blinded by the glitter of too-perfect game plans - the Eagles have suffered their worst defeats (and one tie).
By eliminating weather, a dome could create the perfect storm for a relapse.