PHILADELPHIA --It was a little surprising to see the Eagles’ place in the Pro Football Focus offensive-line rankings this week.

It wasn’t so much that the Eagles were at No. 9 (up from 19th last year), a little lower than I would have expected, but that they were third in the NFC East. PFF ranked Washington (No. 3) and Dallas (No. 4) ahead of the Eagles.

The other interesting aspect: The Eagles were ranked first overall in run blocking, but way down at 18th in pass blocking. While there were some obvious breakdowns over the course of the regular season, that was surprisingly low. If nothing else, Nick Foles’ otherworldly passer rating (119.2) and other achievements suggest a certain level of pass protection.

PFF bestowed its Bruce Matthews Award for the NFL’s best offensive lineman on Eagles left guard Evan Mathis. So it figured that Mathis, with his grade of plus-46.7, would draw praise for “putting on a clinic” at guard. It was similarly predictable that rookie right tackle Lane Johnson would be the weak spot, although Johnson’s in-season improvement was noted, as well.

The staff at Pro Football Focus grades every player at every position based on game film, so this is more than a casual ranking. If the PFF grades are similar to what the Eagles coaches see, it raises the question of whether the offensive line’s continuity is as much of a given as generally believed.

In other words, if the pass protection really requires that much of an upgrade, is Johnson’s expected second-year improvement enough to get it done? Remember, it will also be the second year for Johnson, Mathis, Todd Herremans, Jason Kelce and Jason Peters working together under line coach Jeff Stoutland.

“It will be our second year together as a group,” Mathis said. “We plan to be better than we were this year.”

Or are some of the veterans -- notably right guard Herremans -- not as safe as you might think?

Herremans, Mathis and left tackle Peters are all on the wrong side of 30, so at some point, the Eagles have to begin thinking about long-term plans along the line.

“When we start slowing down, it’s a bad thing,” Mathis said. “Tell me how old I am all you want. It doesn’t really matter. When I slow down, you can tell me I’m slowing down. Until then, it’s really irrelevant.”