Then there's the Reserve/Physically Unable to Perform List, which is also used for the regular season. If by the end of the preseason, a player isn't medically cleared, he can be transferred to the Reserve/PUP, which prevents that player from playing and practicing during the first six weeks of the season.
So if he practices before the first game, they stash him on roster until he is ready and let him practice his way to ready.
If he isn't ready to go or its really close, he's going on PUP.
Bud Adams told me the franchise he admired the most was the Kansas City Chiefs. Then he asked for more hookers and blow.