There are a number of reasons why the 2014 Eagles offensive attack is yet to be as explosive or prolific as the 2013 unit. In no particular order the most common themes are:
1) Teams have a full season of film
2) Nick Foles' regression
3) Issues in the running game
4) The loss of Desean Jackson (to be debated)
I have tackled Points 1 and 3 at the recently. The other thing to note is that the Eagles just haven't been ripping off the explosive plays like they did last year. Missing Desean Jackson could be one factor, but we found several other ways to break explosive plays last year.
For example, last season the Eagles finished with 80 pass plays of 20+ yards and 18 plays of 40+ yards. So far this season, they have 18 pass plays of 20+ yards (on pace for 58) and 4 plays of 40+ yards (on pace for 12).
Read more here.