I don't see any problem with
@Brady6 's idea that Lewis could be cut next year. I am guessing, based on how the RB position usually goes, we won't have an issue of carrying four running backs due to injuries, but it's certainly fair to say that (a) carrying four running backs with a similar style is outside the norm, and (b) based solely on the recent contracts/extensions, Lewis is likely the fourth running back right now. It would be a shame...Lewis has been one of my favorite Patriots for the last two seasons. He is a great story and a great player, but contracts and transactions tell a story.
I've been of the minority opinion that Ninkovich is on the outside looking in, and that was even before the draft. Look at his career arc and age and compare it to Mike Vrabel. Without question, Ninkovich will not be on the team in 2018; his contract was also structured for a minimal cap hit if cut this season.
And finally, I think this is Edelman's last season with the team, and his targets will also be reduced. Edelman will be 31 in a few weeks and check out his completion percentage over the last few years:
2013: 69.5%
2014: 68.1%
2015: 69.3%
2016: 62.0%