20–49: Running backs, fullbacks and defensive backs
50–59: Centers and linebackers
60–79: Defensive linemen, guards, and offensive tackles
80–89: Wide receivers and tight ends
Numbers 0, 00, and 90 to 99 are no longer allowed to be issued, even though these numbers were rarely issued anyway (two players wearing 00 at the time, Jim Otto and Ken Burrough, were grandfathered).
The system would later be modified throughout the years to increase the available numbers to different positions due to increasing team rosters and teams retiring numbers (see also National Football League uniform numbers § Post-1973 changes ).
Other new rules
Defensive players cannot jump or stand on a teammate while trying to block a kick (leverage).
The clock is to start at the snap following all changes of possession. Previously, the clock started on a change of possession when the ball was spotted ready for play by the referee, except if the ball went out of bounds on the change of possession, there was an incomplete pass on fourth down, the change of possession occurred on the final play of the first or third quarter, or either team took a timeout immediately; in those cases, the clock started on the snap.
If there is a foul by the offensive team, and it is followed by a change of possession, the period can be extended by one play by the other team.
If the receiving team commits a foul after the ball is kicked, possession will be presumed to have changed; the receiving team keeps the ball.
Division races
Starting in 1970, and until 2002, there were three divisions (Eastern, Central and Western) in each conference. The winners of each division, and a fourth “wild card” team based on the best non-division winner, qualified for the playoffs. The tiebreaker rules were changed to start with head-to-head competition, followed by division records, records against common opponents, and records in conference play.
Note: Prior to the 1975 season, the home teams in the playoffs were decided based on a yearly rotation. Had the 1973 playoffs been seeded, the AFC divisional matchups would have been #3 Oakland at #2 Cincinnati and #4 wild card Pittsburgh at #1 Miami; the NFC matchups would not have changed, although #3 Dallas would have had to travel to #2 Los Angeles, and #1 Minnesota would have had home field for the NFC championship game.
New Orleans Saints: J. D. Roberts was fired midway through the 1973 preseason. John North served as head coach for the rest of the preseason and the 1973 regular season onward.
The Buffalo Bills added blue pants to be worn with their white jerseys.
The Chicago Bears changed their "C" helmet logo from white to orange with white trim
The Los Angeles Rams introduced new uniforms, reverting their white-and-blue helmets back to the gold-and-blue helmets last used in 1963. The new design included gold pants, blue jerseys with white numbers and white jerseys with blue numbers. Both jerseys included curling rams horns on the sleeves: yellow horns on the blue jerseys and blue horns against yellow sleeves on the white jerseys.
The Miami Dolphins added stripes to their aqua jerseys, while standardizing their white jerseys to include stripes. During their undefeated season, most Dolphins wore white jerseys with stripes, but some did not, including Bob Griese and Larry Csonka. Also, the Dolphins added orange-topped socks with aqua and white stripes.
The New England Patriots added blue outlines to the numbers of both their red and white jerseys. Stripes were also added to the sleeve ends: blue and white for the red jerseys, and blue and red for the white jerseys.
Television
This was the fourth and final year under the league's broadcast contracts with ABC, CBS, and NBC to televise Monday Night Football, the NFC package, and the AFC package, respectively. All three networks renewed their deals for another four years.[2]
Through December 1972, all NFL home games (including championship games and Super Bowls) were blacked-out on television in each team's respective city. The first exception was Super Bowl VII in Los Angeles in January 1973; the league changed their policy to black out home games only if tickets had not sold out. This expanded the league's television presence in teams' home cities on gameday.
The policy was put into effect when, in 1972, the Washington Redskins made the playoffs for only the second time in 27 seasons. Because all home games were blacked-out, politicians — including devout football fan PresidentRichard Nixon — were not able to watch their home team win. NFL commissionerPete Rozelle refused to lift the blackout, despite a plea from Attorney GeneralRichard Kleindienst, who then suggested that the U.S. Congress re-evaluate the NFL's antitrust exemption. Rozelle agreed to lift the blackout for Super Bowl VII on an "experimental basis," but Congress intervened before the 1973 season anyway, passing Public Law 93-107; it eliminated the blackout of games in the home market so long as the game was sold out by 72 hours before kickoff.[3]
With the new rule, the NFL recorded over one million no-shows by ticketholders to regular season games in 1973.[4]
West, 
Central, 
East
West, 
Central, 
East