As someone who watched this team before game 50 of the regular season, I can honestly tell you this:
They do play defense and they work VERY hard at it. Nash is horrible. Thomas is bad. But everyone else runs their asses off to get to their rotation spot, to contest shots, to double, triple and even swarm the lane.
You see, they put a great deal of effort into their defense, but because of a lack of size, get very little out. Because they lack size, they MUST constantly swarm the low post. Otherwise a 7-foot, 240-pound Dirk would just eat up a 6-8, 225-pound Diaw or a 6-7, 220-pound Marion routinely. The open shots they give up stem from this swarm defense. If they had any real size or frontcourt depth, they could man-up or body-up on defense down low. However, they don't, so they swarm, thus they give up open shots and rebounding position as they scramble to cover the open guys/lanes. If they had Thomas and Amare, they would have two 6-9, 250-pound players who are used to playing down low and bodying up the opposition. They would have two solid rebounders in their frontcourt and wouldn't, A. need to swarm as much on defense, thus, B. would be in better rebounding position to thus, C. get more defensive rebounds on first-possession misses to thus, D. Get more first-possession stops.
Their inability isn't weakness and it's not from a lack of trying. They are mortal and can only play to a certain extent.
You can't consistantly ask a wing to muscle up a big. They have. Has it been because they wantred to? No. They went and they traded for a defensiveminded center. Is it because they have to? What other choice do they have? Grant and his two broken knees? Burke and his no-talent?
They are missing their starting frontcourt! You can only expect so much and so far, this team has far exceeded my expectations.
You really haven't a clue, do you?!