Well, it seems like it goes both ways. They sit too far back against short routes, but then against vertical routes down the seams or over the middle, they are too quick to pass the receiver off to the deep coverage player, which results in some pretty massive gaps between the underneath coverage and the safeties/CBs.

Also, some of the zone blitzes do look particularly problematic with defenders sliding over and covering the right areas, particularly when the ball is on the hashmark.