Just read a tweet from Cee Cee this morning predicting we easily win the division with a top 15 D and I agree but we have to be careful a bit with our expectations. Remember we were dead last. Going from 31st/32nd to top 10 may ask too much in one season.
I've posted in a few threads TWO defensive stats I once heard Belichick say he prioritize.......scoring and turnovers. If you recall, the last time our D was ranked in the top coz we kept opponents' TDs to a min.
As for OP question......If our offense picks up where we left off last season with Dak, top 15 D makes us a legit playoff contender, maybe more.
BTW....remember what MM said his overall gameplan was last year........score fast and early, then turn the game over to his DLine.