1. Coaching - I don't know the intricacies of a blocking scheme, but I do know you need to practice to be good at running the ball. The Steelers have become so pass happy they've deemphasized the ground game. The highlight of Cowher's training camps used to be the goal line drill and it was basically offense vs. defense. Battle in the trenches. Offense was going to pound the ball in and the defense is going to try to stop them. It set a physical tone. With Tomlin, they do seven shots which mostly consists of shotgun spread them out, throw the ball. This team has to enter training camp next year with the philosophy and the mentality that they are going to run the ball. That means a LOT of running plays.
2. Offensive line - DeCastro was banged up. Pouncey just doesn't match up against big, powerful IDL anymore. Okorafor is poor at run blocking, not only in physical matchups, but also his processing of the play. This also goes back up to No. 1. These guys aren't conditioned for run blocking. They are used to sustaining blocks for 2.5 seconds or less until Ben gets his pass off. As the season progresses they have fewer and fewer run blocking reps. Look at early in the year when they ran the ball well with Conner. It wasn't perfect, but the more opportunities you give them, eventually the ground games improves.
3. Running backs - They lack vision and take themselves out of plays. Conner is the best, but he seems to press too often. Tries to be a little too much like Le'Veon Bell and not what made him such a successful back in college. Snell isn't much better and McFarland just seems to completely lack any vision. If it isn't the design hole, he's not hitting it.
Again, I fix this by emphasizing it during the offseason and training camp. I'm drafting a tackle in the first round and a center in the second or third. Maybe I sign a stopgap center until the rookie is ready, but I'm not worried about a rookie starting. We've seen a lot of success over the years with young offensive linemen around the league. Then I'm drafting Williams or Gainwell in the second. Williams is a do-it-all back who can make defenders miss. Gainwell sat out the season so we haven't seen him as much, but he has big-play ability and is an asset in the passing game.