There is really a limit to what an interim coach can do. He takes over a team and playbook that his predecessor used. Given that, I think it is pretty amazing the changes Callahan has made. Gruden thought there was no role for Peterson in game 1. Peterson is now the centerpiece of the offense. Callahan took an offense that could not run the ball and made it a running team. The defense is playing much better. And the number of penalties has dropped an incredible amount.
That said, it is not clear a power running offense will win many football games. No touchdowns in 13 quarters is pretty brutal. I still think the team is basically handicapped with Case Keenum, Colt McCoy, and a very green rookie, Dwayne Haskins at qb. This team is not in a win now mode. And it wasn't coming into the season. Which makes not trading players away at the trade deadline or even last off season very perplexing.