I'd put some of that on the talent / skill set / experience of our WRs, TEs and RBs.
As great a season as John Brown has had, he's somewhat limited in the routes he can run. Same with Beasley. We've got no credible third WR, so that option is kaput. Gore can only run between the tackles, so that makes defending him easier. Singletary and Knox are more versitile but as rookies, McD is going to have them on a leash.