In re-watching this last game ( thanks NFL rewind ) one of the things I've noticed is that David Johnson (85) and Weslye Sanders are really killing us on some running plays. Not only do they get beat clean on many of their attempted blocks, they also completely blow assignments and run right by the guy they're presumably supposed to block, leaving them untouched to have a clean tackle on the ball carrier.
I was never the biggest fan of Spaeth, but I noticed last year that his blocking had really come a long way,to the point that I think he was a well above average blocking tight end, though his hands never were that great.
Anyway Matt certainly had some struggles as a blocker early in his career, so maybe one or both of these guys will start to get it in time. But as of now I'd have to label David Johnson in particular as one of the main culprit's in the current inept state of our running game.