Why didn't the Eagles use James Casey?

The Eagles used many different schemes vs the Redskins but one player that they went after in free agency, Tight End James Casey didn't play a single snap at offense. I don't understand exactly why he didn't play, obviously they want Celek and Ertz on the field and rightfully so. Celek had a big time touchdown and some nice receptions as well as Ertz grabbing a nice pass and good pass protection. Casey is a versatile guy everybody knows that, so why no FB, Slot WR, and especially a three tight end set which we did not see last night. It could help out the Eagles stay fresh with the fast pace offense and they are paying Casey a lot of money not to play offense and only special teams. I believe Kelly will put in some plays this week for Casey and perhaps some 2 tight ends split wide and one on the line type formations. Just a thought but philadelphiaeagles.com Adam Caplan (NFL Insider) also noticed Casey was not out there but made two tremendous plays on special teams. If the Eagles don't get Casey out on the field often, it will be very puzzling to say the least. A talented player that could line up anywhere should be able to fit in a college type system like the one Chip Kelly has in place.