An undroppable player in fantasy football is a player that cannot be "dropped" by the manager of a team, meaning the player cannot be released into free agency where other teams have the opportunity to add the player without compensation.
Following the draft, team managers are given a list of undroppables, which contains every player that cannot be released outright and must be traded in order to change teams. Undroppable players are a mandatory setting in public leagues. While the commissioner of a private league can choose to disable this feature, many elect to keep it and maintain a level playing field across the league.
Undroppable players are generally star players that have a reputation for putting up strong fantasy numbers year after year. Other undroppable players include those coming off widely successful seasons in the previous year. Most fantasy football teams have at least one undroppable player that can be relied upon to keep the team afloat when other players are struggling. Below is a list of the players that are currently undroppable heading into the 2020 fantasy football season.
Rules surrounding undroppable players exist primarily to prevent collusion. Without a list of undroppable players, two well-acquainted managers could strike a deal in which the manager of a struggling team drops star players so that the manager of a contending team can scoop them up and drastically increase their chances of winning the league, and possibly a large sum of money.