The science of creating over/under lines for NFL games is not as arcane or mysterious as it might seem. It’s typically based on a fairly rudimentary mathematical formula, with the teams’ projected combined total yardage serving as the key element.

Hey, all right! With that knowledge in hand, now all we have to do is accurately predict the total yardage for each team and we’ll be on our way to breaking the bank. (Or “destroying your bookie.” Choose your favorite infantile tout cliché.)

In the first week of the coming NFL season, I’m keeping an eye on two games in particular that have seen their over/under (or “total,” in betting lingo) drop since the odds were first posted for wagering. I don’t think the line is coming back up in either case. At least three of the four teams involved are likely to struggle in the total yardage department.

In the Steelers-Broncos game scheduled for the evening of September 9, the total opened as high as 45.5 in Las Vegas sports books before falling to 45 or even lower, depending on where you shop. I agree with line move, despite the high-powered reputations of opposing quarterbacks Peyton Manning and Ben Roethlisberger.

Manning could very well end up having a fine season, but he figures to have a ton of rust after missing the 2011 season. Denver’s defense, particularly a secondary led by safety Mike Adams, is expected to improve under newly hired coordinator Jack Del Rio.

I could see Pittsburgh offensive coordinator Todd Haley, another new hire, establishing a slow, steady pace, running the ball often and allowing Roethlisberger to pick his spots. (A rush-oriented offense is often good for “under” bettors because it tends to chew up the clock.)

I’ll predict a final score of 21-17. Who wins? Who cares? We’re betting totals here.

In the Eagles-Browns game set for earlier in the day, the total opened at 42.5 points in Las Vegas and has fallen to 41.5 in most spots. It’s highly unlikely rookie quarterback Brandon Weeden will find any kind of a rhythm against a blitz-happy Philadelphia defense. Watch for the Eagles to build a lead, then protect it by relying on the rush.

I’ll predict a 24-10 final in favor of Philly, largely because I’m so bearish on Cleveland in this matchup. I’ll also consider including the Eagles as one leg of a two-team, six-point teaser.