I'm not saying they need a great LT. Houston just traded away a Pro Bowl caliber LT to Seattle but the price is probably too much for Philly given the fact that they don't have a 2nd or 3rd round pick in next year's draft.
I'm just talking about a serviceable OT. Vattai has looked like garbage to me from his extended playing time last year during Lane Johnson's suspension and last week against San Fran. Like BisonFan02 said Lane Johnson can move to LT if they find a good RT that a team is willing to part with.