Players who fail their physicals are put on the physically unable to perform (PUP) list. They count against the 80-man roster and are eligible to practice whenever the team clears them.
Typically, they are players who are coming off surgeries related to previous year injuries, players who were injured during off-season workouts and players who were injured while working out during the month off prior to the start of camp.
The Packers can also pass a player on their physical and still hold them out if they choose. In most cases, it is someone with a minor ailment who they prefer sit out a day or two.
JSOnline Blog  wrote: