Why are the Eagles 5.5-point favorites?

Our weekly look at the Eagles' line with Dave Staley of sportsbook.com:

Q: What's the line for the Birds' matchup with the Falcons this weekend?

A: Huge game for the Eagles this Sunday as they head to Atlanta as 5.5-point favorites. We actually opened the line at the Eagles minus-6 but later adjusted it to minus-5.5 on Tuesday.
The Eagles being generous favorites on the road against a potential playoff team has everything to do with the health of some key Falcons players. First and foremost, QB Matt Ryan has already been ruled out, and Chris Redman will get his first start of the season.
Redman looked good last week, throwing for 243 yards and a couple of TDs, without being picked off. In 2007, when he played in seven games, Redman threw 10 touchdowns, five interceptions and had a QB rating of 90.4.
If Ryan was healthy, the Eagles would have probably been right around a one-point favorite, so I’m a little concerned that 5.5 is too much.
Meanwhile, Michael Turner appears to be a game-time decision with a bum ankle. If Turner can’t go, Jason Snelling and Jerious Norwood will share the ball-carrying duties. Although neither have Turner's abilities, both do some good things, and their legs should be fresh, which is always important for a RB this time of season.
If the Eagles are without DeSean Jackson, which appears almost a certainty, it probably cancels out Turner being sidelined for Atlanta.
It's hard to judge whether this line will move anymore. Since 75 percent of the money is on the Eagles, this one could move back to six points, but I highly doubt it will go any higher. If you like Atlanta, I’d wait to see if it goes to six, especially considering that the Falcons are 4-1 against the spread at home this year.

Q: What about the over/under?
A: The total hasn’t budged after opening at 44 points. Even though there are plenty of injuries on the offensive side of the ball, many of the back-ups are experienced and capable of getting the ball in the end zone so I think this total is about right.
So far, 78 percent of the money is on the over, which isn’t a surprise as that's the side usually favored by the betting public. Come to think of it, I think the betting public has backed the over in every Eagles game this year.

Philly averages 26.6 ppg, good enough for seventh in the NFL, whereas Atlanta scores 24.7 ppg, eighth in the league.
Over bettors might also realize that Atlanta’s defense has given up a ton of points recently. In their first five games, the Falcons have allowed an average of just 15.4 ppg. That number skyrocketed to 28 ppg over their last six games. The over covered in five out of those six games.
If you agree with the public and are going to back the over, you better get it now because I could see it going to 44.5 or even 45 by kickoff. As any sharp bettor will tell you, handicapping the game is only half the battle. Getting the best number is almost as important.