Don't blame it on small ball.
This team has been able to lock other teams down defensively with linueps that included the likes of Posey and Pietrus at the 4.
Furthermore, let's not pretend that our current starting lineup (and the one from last year) is really anything but small ball to begin with. Bass is an undersized power forward barely bigger than Paul Pierce who provides no shot blocking, no post game, and on a good day is an average rebounder. And we were a very good defensive team with Bass manning the 4 last year.
With the way some people are whining about Green at the 4, you'd think we were subbing him in for Kevin McHale.
That's not to say that Green isn't to blame. He needs to be better on defense, but so does the whole team.
But it's not because of small ball, it's because the defense of the players on the court simply isn't up to par.