Boozer was never injured in practice. I have no idea what you are talking about.
Ellis had a freak injury in practice...guess how many games he missed? ZERO.
He only missed a few practices. There is not much intensity to practice games, there really is no reason for 2 week injuries to be happening in scrimmages.
Boozer was injured in the preseason last season. Fractured his hand.
DWade was injured in a preseason game last year and missed a couple of weeks. It happened early enough that he didn't miss any regular season games.
Jerebko for the Pistons missed the entire season after a ruptured Achilles Tendon in the first preseason game.
The point is, injuries don't just occur in 'real' games.