<P> During the preseason, numbers outside permitted ranges (usually single digits) may be worn if there are no numbers available within the range for certain positions, usually wide receivers or backs . </P> <P> Many NFL teams have retired some numbers in honor of the team's best players . Generally when a number is retired, future players for the team may not wear it . The NFL officially discourages (but does not prevent) teams from retiring numbers, as the limited number of uniform numbers available for each position can be depleted . Some teams will hold official "number retirement" ceremonies, others have "informally" retired numbers by simply not issuing them . For teams that do not retire uniform numbers, they often honor players in other ways, such as team halls of fame or the like . </P> <P> Numbers 0 and 00 are no longer used, though they were issued in the NFL before the number standardization in 1973 . Quarterback Johnny Clement, running back Johnny Olszewski and safety Obert Logan all wore a single - 0 jersey in the NFL . Author George Plimpton famously wore 0 during a brief preseason stint at quarterback for the Detroit Lions . Jim Otto wore number "00" during most of his career with the Oakland Raiders as a play on his name, "aught - oh ." Wide receiver Ken Burrough of the Houston Oilers also wore "00" during his NFL career in the 1970s . More recently, linebacker Bryan Cox wore 0 in the 2001 preseason with the New England Patriots; for the regular season, he switched to 51 . Numbers from 01 to 09, with a leading "0" digit, would theoretically be allowed (and be considered the same as numbers 1 to 9 for record - keeping purposes), but such a number has never been issued in professional football . </P>

When does the nfl officially confirm jersey numbers