No one is guaranteed anything in the NFL. The list is monsterous and full with top picks that never made it. And in reality, only after one game, you have still to keep a close eye on the rooks even one as talentad as Sean Taylor. So no dead lock guarantees can be granted just yet. I'll admit, he is good but who really knows.
As for Earl, I think that the Texans saw Antonio Gates catching everything in site with no answer from Brown. Maybe Earl can provide something that Brown cannot. Earl will be the starter next year and perhaps the practice move is a way to prepare him for the eventual switch. Earl may even move into the position as soon as the coaches see that his knee has fully recovered.
Cant complain though, either one of these two Strong Safties is a tub load better then Matt Stevens. Imagine what the Chargers would have done to us if he was still in the secondary starting rotation. That guy couldn't tackle a laundry basket.