During the season, a team may have a maximum of 20 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 20 player active roster, each team has 1 Injured Reserve slot. A player may be placed in the Injured Reserve slot under the following conditions:
1. The player was placed on the NFL’s Injured Reserve for that season (and is thus out for the season)
2. 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.)
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 agent. 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 11 players:
1 QB
1 RB
1 WR
1 TE
3 FLEX (these may be RB or WR)
1 K
4 D (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).
(In 2007, there will be 5 D starters)
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).