American football positions four linebackers, and four defensive backs (two cornerbacks, a strong safety, and a free safety) Special teams are units that are on the field during kicking plays. While many players who appear on offensive or defensive squads also play similar roles on special teams (offensive linemen to block, or defensive players to tackle) there are some specialist roles which are unique to the kicking game. American football positions In American football each team has 11 players on the field at one time. The specific role that a player takes on the field is called his position. Under the modern rules
Comparison of American football and rugby union front-row forwards). Rugby teams may make up to seven substitutions. Each team must field 15 players at the start of each match. Players who are bleeding may receive medical treatment off pitch and are replaced until they have stopped bleeding. If the bleeding has not stopped after 15 minutes of "real time", the player will be permanently substituted. This can be down to officials' discretion, depending at which level the sport is played, where only minor medical assistance is needed to make the player fit to return to the field of play. Ejected players in American football can be replaced