Something to keep in mind about Boston's recent defensive play - while a good deal of it is related to the totally new rotations being used, some of it clearly comes from the level of competition and the time of year it is.
Inujuries have taken a toll on depth, so a portion of this team's lack of defensive intensity is caused by the heavier minutes, but part of it is simply standard March basketball in the NBA.
Celtics fans were spoiled last year, as Cleveland fans are being spoiled this year - most team's do not play 100% effort-wise for 82 games. When teams get in the dog-days of the season they tend to pick their spots - this has been evident with Boston the past few weeks as they've saved their defensive push until the 4th quarter and basically tread water until then.
We may not like it as fans, but an 82 game season is long and with minutes piling up and age being a concern, Boston is going to choose its battles until the stretch run with a healthy team.
Last year none of these guys had proven anything - much like Cleveland this year - so there was an urgency about going for the 'chip that drove them each and every game. Though HCA is important, its not close to the same level of urgency created by a legacy-drive toward the title...as such, Boston will have games like the other night vs. the Nets, where it is devoid of energy and life until very late in the game - sometimes that costs the team a game - a fact of NBA life.