There are a lot of story lines to keep track of as the Eagles enter preseason play this coming week, here are a few of the most pertinent things to watch for when the birds take the field, for both them, and their opponents.

Undoubtedly, the first thing on many fans minds is the health-and performance-of Sam Bradford. The Birds are all in on Bradford. If he doesn't pan out, their second round selection and Nick Foles are gone for nothing. 

Right up there with that then, is both the emerging offensive line, apparently solidified save right guard, and Zach Ertz' improvement as a blocker. With Bradford's injury history, the performance of the men protecting him will be key.

On the other side of the ball, the Eagles' retooled secondary will be in flux. We can watch for both the starters that emerge at cornerback and safety, as well as to see how new $63 million dollar man Byron Maxwell plays without the Legion of Boom surrounding him.

Game 1: Indianapolis Colts, Sunday, Aug. 16, 1:00 PM 

(2014 Record: 11-5, lost in AFC Championship)

There will be a lot of familiar faces when the Eagles meet the Colts in their first preseason game. Their two longest-tenured players prior to this off-season, guard Todd Herremans and defensive end/linebacker Trent Cole, will be suiting up for the other team.

To add to that, running back Frank Gore, whom many thought was about to be announced as an Eagle this spring, is a Colt instead. Those three are part of a massive free agent haul by the Colts that also includes receiver Andre Johnson. This was the Colts' window to spend big before they have to make Andrew Luck possibly the most highly paid player in the game.

Yet, they ignored some of their weakest positions, mostly on defense, and lost defensive end Cory Redding. One player to watch when the teams play is rookie fourth round pick Clayton Geathers, who is turning heads and might be the safety the Colts need to shore up that defense.

Game 2: Baltimore Ravens, Saturday, Aug. 22, 7:00 PM

(2014 Record: 10-6, lost in Divisional Round)

The Ravens saw a lot of turnover this off-season. Wide receiver Torrey Smith, defensive tackle Haloti Ngata and linebacker Pernell McPhee are all gone. They did manage to bring breakout veteran running back Justin Forsett back.

It will be interesting to see who is stepping up in the receiving game with Smith and tight end Owen Daniels gone. Veteran Steve Smith is there and should be the leading target again, but beyond him it gets a lot younger and a lot murkier.

The Ravens first round pick, Central Florida receiver Breshad Perriman, could be a real game changer. A player many Eagles fans had on their minds when the team walked to the podium in May, Perriman has deep speed to spare but has struggled with concentration drops. If he can fine tune his game for the NFL, the Ravens might not miss Smith much at all.

Game 3: Green Bay Packers, Saturday, Aug. 29, 8:00 PM

(2014 Record: 12-4, lost in NFC Championship)

Don't get too excited if the Eagles' overhauled secondary starts intercepting a bunch of Aaron Rodgers throws - the same has been happening through Packers' training camp. It's just Rodgers purposefully throwing contested balls during practice to force his receivers to make a play on the ball.

The Packers had a fairly quiet off-season. Wide receiver Randall Cobb was arguably the best free agent receiver available with Jeremy Maclin, but unlike Maclin, he stayed home. 

During the past two drafts the Packers have spent their first round pick on safeties Eagles fans had in mind: Ha Ha Clinton-Dix in 2014 and Damarious Randall in 2015. Randall and second round pick Quinten Rollins are reinforcements to replace several outgoing members of the secondary.

They also drafted UCLA quarterback Brett Hundley in the fifth round, much later than many expected he would go. Hundley is a dual-threat qb many had projected as a fit for Chip Kelly's offense. Kelly attempted to recruit Hundley when he was at Oregon.

Game 4: New York Jets, Thursday, Sept. 3, 7:00 PM

(2014 Record: 4-12)

Even if you were a fan of Rex Ryan, it's hard to be too upset with the off-season the Jets had: They brought cornerbacks Darell Revis and Antonio Cromartie home. Leonard Williams, considered by many the best player in the draft, fell into their laps at pick six.

Williams will get his chance early to step up on the defensive line following the four game suspension of Sheldon Richardson for marijuana that may yet be extended because of street racing.

There was speculation the Jets were interested in Marcus Mariota - or any quarterback - to compete against Geno Smith, but Smith enters camp as the undisputed starter. The arrival of Brandon Marshall from Chicago gives Smith the best target he's ever had to throw to. 

The Jets' second round pick was another weapon and another Smith, Ohio State wide receiver Devin Smith, whom many projected as a target for the Eagles. Devin Smith likely won't be on the field this preseason however, after suffering a rib injury.