"Defense and rebounding" require, more than anything else, "focus, effort and desire". WE lack the altter on a large scale on most nights.
These guys are completely oblivious to where anyone from the opposing team is on most rebounding opportunites. Guys are flying by or around them and they have no idea where they're coming from, it's pathetic.
I think it has very little to do with athleticism. Even if they have slowed down it shouldn't be that dramatic a disparity in speed and quickness.
Besides, Bird was never quick or fast but he was a good rebounder up until he retired.
It'a effort, focus and desire on both defense and rebounding.
That's why I'd dole out my big man minutes right now based on who's the most aggressive on the boards and I'
d tell them that's how it's going to go.
I would also spend an entire week of basketball 101 on rebounding to sort of humiliate them with rebounding drills in practice, all day, every day, for a week.