It is important to have more than one nickel front and especially against Brady and the pats. Being able to flex Von and shift the line along three down LM is important, but so is also having 4 DL occasionally to create different matchups.
The key is having flexibility in how you matchup, knowing what weaknesses that produces, and running plays in those formations that help your matchups and cover your weaknesses. That is where DEN got exposed against NE last year. They did not gameplan to stop the run effectively, and got left high and dry as a unit because they could not come up with plan B.
DEN played them early, and they were simply not far enough along as a unit to stop them! They got much better as the year progressed, but reverted to stupidity against BAL at home. They were not prepared to take away the deep ball schematically or by gameplan. Once BAL started playing chuck it deep ball, they failed to compensate or adjust accordingly.
Occasionally, you are just going to get beat when the matchups do not favor you and you do not play well or smart. However, the more I watched the games DEN lost, they did not adjust accordingly or have flexibility in the gameplan. The last 3/4 of the season they were simply brilliant in this regard. So, they just did not come prepared against BAL and I am sure they will be much more prepared in year 2. Including having a run front in the nickel and variability with gap responsibilities and added pressure packages.