In order to get on the injured reserve list, the player must have passed a physical test before the start of the season. When placed on the injured reserve list, this typically means the player cannot return during any point during the regular season.
The injured player can be replaced on the roster by another man. Although uncommon, one player is permitted to be removed from the injured reserve list and put back in the game per season, instead of staying off the field for the entirety of the season.
Players on the injured reserve do not contribute to the team's maximum amount of players.
There are two types of ways that players can get on the injured reserve list. One way is if a player is injured in a previous season or training season and is no longer able to play in the following. This is known as being "physically unable to perform." There is also "non-football injuries," where a player is injured from activities not related to football.
Minor injuries can also put players on the injured reserve list, but they are to be taken off once they are cleared.