I was sifting through some data at Football Outsiders and took a look at the offensive line statistics . The methodology seems quite complex and there are certainly items during a football game that cannot be quantified, but the stats paint a picture of the effectiveness of the guys in the trenches.
Unsurprisingly, the Steelers offensive line ranks 24th in run blocking and 30th in pass blocking. The O-line might be slightly better if the team wasn't without its best running back for most of the season and didn't have a quarterback that holds onto the ball too long. That said, these rankings are pretty consistent with what I've seen watching the games. One of the categories FO uses to rank O-lines is called "Stuffed." It's basically the number of run plays that go for negative yards or don't gain a first down on a 2nd (or 3rd or 4th) and short. (This is very simplified. Go to the site for exact calculation.) The Steelers are stuffed on 30% of its running plays, which is good for 31st in the league, ahead of only the Philadelphia Eagles.
The other statistic that interested me was the success of running plays by direction. When Pittsburgh runs left, it gains 5.65 adjusted yards to the left end (a run outside the tackles) and 4.77 yards to the left tackle. Both are in the top ten in the league. These figures are by far superior than running to the middle (3.91), to the right tackle (3.36), and right end (3.53). This is unsurprising. The Steez best run blockers are Max Starks and Kemo, who anchor the left side of the line. Kendall Simmons and Willie Colon are pretty terrible on the right side, where we struggle to run the ball. Darnell Stapleton is better than Simmons, but isn't a powerful run blocker. Among hard-core Steelers supporters, this is pretty much common knowledge. So based on these statistics, you would think the majority of carries would go left, behind the strength of the line. Well, you would be wrong. Right now, only 17% of carries are going left. 56% are going up the middle. 27% are going to the right.
Here is my attempt at reasoning why we run more to the right than to the left. Arians knows that the left side of the line is better. He knows that our opponent knows that our left side is better. Since the opponent knows, he should run to the right to surprise them. This seems to me to be Arians model of thinking. He would rather try to surprise than play to the teams strengths.