Our O-Line is terrible. We got no push, so Grant wasn't going anywhere, couldn't protect Rodgers either. McCarthy should have realised that last season (when Rodgers had to scramble out of the pocket so much) he was in need of better O-Linemen. We've been very lax in drafting anything high up for the O-line. Hence why our running game has sucked for quite a while now.
EDIT: I need time to cool off, so don't read my comment as gospel, I'm just pissed. We'll get better im sure.