in b4 suddenness and glide
You're right, he doesn't do anything that's really "different" there. It's not like he's going out on 20-yard routes and making plays that a receiver would make.
What he DOES do is turn short dump-offs into 10-yard gains better than any other running back in the league right now, and right up there with any running back ever. He does pick you up a buttload of first downs and keeps drives going, which is extremely valuable. But as you said, it's not like he's breaking new ground by doing that. He's just playing the running back position at a very high level.
If I could keep him on the team, I would, but it wasn't really up to us. Even if we offered him the $17 million he was asking for, I don't think it would've mattered; I don't think he was going to re-sign for any price.