I have been thinking about this a lot recently. My question isn't can this current team be a good defensive team - the question is a lot broader than that. Can a running team that pushes the ball everytime, that plays a fast tempo offensively, can they then go to the other end of the floor and get down and dirty as you must do to be a good defensive team.
I think it is nearly impossible - I can't think of any really good defensive teams that ran. Lakers of the 80's is the only team that maybe did. But the Lakers also if they didn't have a fastbreak played a very patterned and patient offense. The Bulls in the 90's actually ran very little.
It is difficult for players to play at 90 MPH on offense, take quick shots, run around, pass the ball - call it whatever you want. But then to ask those same 5 guys to run back to the other end and dig in, be patient, play together, be patient, play as one, follow the gameplan. it is impossible. So I think the way you play at one end impact the other end - if you play a helter - skelter style offensively - then that is how you are going to play defensively. That is why the really good defensive teams are not fastbreak teams - you are asking too much of NBA players in a season that is 82 games long.
So if O'Brien who I still like a lot - if he doesn't change the offense, if he doesn't bring some discipline, some calmness, some normalcy to the offensive end the defensive end won't ever improve. yes we have some glaring defensive weaknesses - but I am 100% convinced that if we ran a more patient offense, our defense would be much better - even with the same exact players and even with the same exact defensive system. This is the same exact defensive system OB ran in Boston and Philly, what has changed is the offensive system - that is the problem right now.
Edit: I hate to bring football into this discussion, but compare offensive football players to defensive players. The mentality is completely different, the approach is completely different. But in football you have two sets of different players, in the NBA you have the same players trying to play both sides at the same time - it is a difficult transition that is made much more difficult when the offense is so helter - skelter