As we've poured over the Eagles needs in free agency and the draft, one position that hasn't come up much is offensive line. We've all pretty much agreed that bringing back Evan Mathis was a priority to keep the line that had played so well consistent.

Then, I came across this free agency preview from Bill Barnwell, formerly of Football Outsiders and now of Grantland.

Top priority: Finding a left guard to lock in their offensive line

After all the hype last year, the Eagles failed because their play at the line of scrimmage wasn't up to snuff. In particular, Philadelphia's offensive line was a patchwork group that never played a single down as the five-man unit the organization expected to use throughout the season. Repairing that line should make Michael Vick healthier, DeSean Jackson more effective, and that dismal goal-line performance a thing of the past.

I'm not entirely sure what Barnwell is talking about here. Unless he's referring to the 5 guys the Eagles expected to start prior to the season, they absolutely started the same 5 for the majority of the year. After Danny Watkins took over at RG in early October, the unit was stable.

Now, he says the play of the line "wasn't up to snuff." This is in direct contrast to what Pro Football Focus saw, who ranked them as the 2nd best offensive line in football.

Blocking for Michael Vick isn’t always easy, but the Eagles did a great job of putting him in a position to succeed. The left side in particular was superb, forming one of the best tandems we’ve graded since the inception of Pro Football Focus (earning a combined +62.2 grade). There were some issues at the right guard spot, and you wonder if Todd Herremans (+2.4) is best served protecting anyone’s blindside, but this line has it in them to dominate.

And particularly, they ranked Mathis as the 2nd best guard in the league last year. On the other side, Barnwell says that upgrading LG should be the Eagles top priority.

So who to believe? We've got arguably the two big internet based football stats sites pitted against one another here. Barnwell is no longer with Football Outsiders, but presumably he still uses similar evaluation techniques. How could he and PFF seen such opposites?