I actually saw DTs adjust to FredBeard this year. If they could go chest-to-chest with him - he was having trouble at times anchoring. If he gets his arms extended he excels. Smith was better in '13 than he was in '14. From what I saw it was Martin and Leary who really took big steps forward. Martin was best guard I watched this year. Many of us under-valued the guard spot as you usually don't draft guards early. Martin has changed my mind entirely about the position because as we saw the guard position was main reason for this team going to playoffs.
I spend an excessive amount of time watching and re-watching the OLine. To me the #1 thing was the commitment to running game.
This OL scheme with a large amount of Zone Blocking requires a large number of carries to function properly. They have many runs that don't really do much, but they use the repetition to get defenses guarding against one thing and then come back with something else. Some games they'll repeatedly run the zone stretch left with only moderate success and then they'll throw in an occasional power blocking run to the right. The defenders will get themselves out of position trying to get a jump to the left and then that power run right will gash them. The details and intricacies of the running game, especially the zone blocking scheme are vast. Sometimes the OL and the RB are keying on things as simple as a defender taking 1 additional step in one direction from when they ran a particular play the 1st time to the next time.
When I mention Fred being a 2nd year player, it's not just his own ability, but he makes the line calls and in the running game what he sees and calls can make a big difference.
This being the 3rd year with Callahan's scheme is also helpful. It takes time to fully implement the Zone Scheme and they run more than just zone. They continually throw in a new wrinkle here and there.
The difference in a big gain and a minimal gain in the running game is often just a matter of a few inches. A defender gets his head to one side of the OLineman or he doesn't and that just enough difference on some plays.
I don't want to take anything away from Martin because his performance as a rookie has been amazing; however, attributing all differences between 2013 and 2014 to him would be an exaggeration.