I agree that without Revis, the Pats cannot play defense the way they did in 2014. I just don't think they necessarily have to.
Mayo, you and I have disagreed about the level of play of the defense last year. You have said that they were as good as any team in football and I don't think they were. I saw a team that allowed too many points to too many mediocre offensive teams to rank among the very elite. To me, while they were the best Pats defense in a decade, they were still susceptible to the run and had difficulty pressuring the qb. While I saw these as pretty clear deficiencies, they did make plays when it mattered most. Against the Ravens and the Seahawks they were exposed, but ultimately made the big plays necessary to win (even if both big plays occurred in their endzone!). To me, that was the big difference between the team last year and the teams that lost in 2007 and 2011.
I think the reason they were able to make those plays was the maturation of their younger players and, most importantly, the addition of playmakers. Previously, our best defensive players (guys like Mayo) were excellent but not playmakers. Last years team, with Collins and Hightower and Browner and Revis, the Pats had players who could make big plays, and even when they themselves weren't making big plays, they were players who needed to be "accounted for" by the opposition, players BB could scheme around and thereby make everyone else better (BB has been doing this on offense for years, first due to Brady but also with Dillon, Moss, Gronk, Hernandez, et. al.). If we lose Revis and subtract such a difference maker, then we better add one somewhere else. Maybe Easley will be such a player, but without Revis we need to add somebody who can allow BB to use his mad scientist touch to make this defense capable of making big stops at important times. This is why I have pushed so hard for Suh if Revis is unsigned. I think BB could then turn this defense into a front seven oriented defense that would be Superbowl calibre. They wouldn't be able to play defense the way they played defense last year, but the might end up just as good.