Is This Defense Good Enough?

I have no doubt that Ben and the offense can put points on the board, but the axiom is that defenses win championships. I wonder if this one is good enough. Granted they have been improving as the season went on, but yesterday's game against the 1-15 Browns was really disturbing. Huge chunks of yardage given up all game. Without a fumble at the 1 and an interception in the end zone, we don't win that game. Even after we go ahead with less than 5 mins to play, the Brownies easily go downfield to tie. I believe we can beat Miami and KC but Brady will eat us up if we play like we did yesterday.
Kudos to the offense because of all the people not playing, but that wasn't the case on defense as only our 38 yr old miracle guy didn't play. I hope I'm wrong, but I remain worried.