https://en.wikipedia.org/wiki/Physically_unable_to_perform
Preseason PUP[edit]
A player who, as a result of football-related injuries, is unable to take part in
training camp practices may be assigned to the preseason PUP list. Players can be moved off the PUP list to the active roster at any time, even after one practice. A player cannot be placed on the PUP list, however, once he has taken the field for a practice, even if only for a few minutes.
Regular-season PUP[edit]
A player who finishes the preseason still on the PUP list can then be placed on the regular-season PUP list. Such players must sit out the first six weeks of the regular season. At that point, teams have a five-week window in which to allow the player to begin practicing; from the day the player begins practicing, teams have an additional 21-day window in which to decide whether to activate the player to the 53-man roster. If either of those deadlines pass, the player must remain on the PUP list for the remainder of the season.
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Non-football injury[edit]
A similar list, known as the "non-football injury" (NFI) list, is functionally equivalent to PUP, but is used for players who are unable to practice as a result of conditions unrelated to football, or injuries that did not occur during a game or practice. For example,
New England Patriots tackle
Marcus Cannon began his rookie season on the NFI list as he recovered from
chemotherapy for
non-Hodgkin lymphoma. Also,
David Quessenberry of the
Houston Texans was put on the NFI list in mid-June, 2014 after being diagnosed with
non-Hodgkin's lymphoma at the age of 23.
The NFI designation, despite its name, also covers injuries sustained during football played outside the NFL, including
college football.
Willis McGahee spent his entire rookie season on the
Buffalo Bills' NFI list due to the major knee injury he sustained in the
2003 Fiesta Bowl.