It doesn't take much talent to play defense, just effort and attention to detail. If you can read the offense, stick with your man and keep your hands up, you're good. Thomas didn't enforce this. He was too caught up with his own bullshit. Marbury had one of his best defensive seasons two years ago and Crawford had a good one three years ago when Brown was coaching. A new voice that doesn't mind benching Richardson and Curry (if not trading them) and understand the ins and outs of defense can change this team. With a few trading tweaks the Knicks can become competitive again.
If we keep Marbury the best bet is to keep Crawford and Randolph unless some fool of a GM is willing to give us young talent for him, trade Curry for a defensively competent center. The right coach can work with Randolph's defensive wows. Curry is hopeless.