During the season, a team may have a maximum of 22 players on its roster. A team is not required to have a roster which contains a valid lineup (i.e. if a team wishes to cut its only kicker, it may do so).
In addition to the active roster, each team has 2 Injured Reserve slots. A player may be placed in an Injured Reserve slot under the following conditions:
1. The player was already on the team’s active roster. (A team may not pick up a player from waivers or free agency and place them directly on Injured Reserve.)
and one of the following conditions:
2A. The player was placed on the NFL’s Injured Reserve for that season (and is thus out for the season) or
2B. The player was placed on the NFL’s Physically Unable to Perform list at the start of the NFL season. Note that training camp/preseason PUP is a different thing and does not apply. A player on PUP at the start of the regular season means the player cannot return to action until midway through the regular season.
If an ineligible player from a team’s active roster is wrongly placed on Injured Reserve (i.e. a player who is listed on the NFL Injury Report as Out, but is not officially on IR), the move will be undone by the commissioner. If the team had also added a player to the active roster to fill the spot from waivers or free agency, the player will be returned to waivers or free agency. If that player was a waiver wire pickup and someone else had bid on that player, the commissioner will manually re-do any waivers that occurred after that, in order to make it how it would have been if the illegal waiver claim not been made.
Once a player is placed in the Injured Reserve slot, the owner may waive or trade him if he desires. Otherwise, he remains there until the Keeper Deadline (see Keeper Rules).
A team’s starting lineup may consist of a maximum of 13 players:
1 QB
1 RB
1 WR
1 TE
3 O-FLEX (these may be RB or WR)
1 K
1 DL
1 LB
1 DB
2 D-FLEX (these may be DL, LB, or DB)
There is no penalty for a team including fewer than the maximum number of players in its starting lineup (other than the obvious).
Players may be started, benched, waived, signed, or traded up until 5 minutes before the start of their game. At that time, they freeze until that week’s games are over (see Transaction Rules).