<P> The 1972 NCAA University Division football season saw the USC Trojans, coached by John McKay, go undefeated and win the national championship as the unanimous choice of the fifty AP panelists . Eighth - ranked in the preseason, the Trojans were narrowly voted #1 in the first AP poll, and stayed out front for the rest of the year . </P> <P> During the twentieth century, the NCAA had no playoff for the major college football teams in the University Division, which became Division I in 1973 (and Division I-A in 1978). The NCAA Football Guide, however, did note an "unofficial national champion" based on the top ranked teams in the "wire service" (AP and UPI) polls . The "writers' poll" by Associated Press (AP) was the most popular, followed by the "coaches' poll" by United Press International) (UPI). Through the 1973 season, the UPI issued its final poll in early December before the bowls, but since 1968 (and 1965) the AP Trophy was withheld until the postseason was completed . The AP poll in 1972 consisted of the votes of fifty sportswriters, though not all of them voted in every poll . Those who cast votes would give their opinion of the ten best teams . Under a point system of twenty points for first place, nineteen for second, etc., the "overall" ranking was determined . </P> <P> This season was historically significant because it was the first in which freshmen were eligible to play varsity football in the University Division . The NCAA had historically prohibited freshmen from varsity competition, except during the United States involvement in World War II . In 1968, the NCAA allowed freshman eligibility in the University Division in all sports, except football and basketball, and extended the rule to those sports effective with the 1972--73 academic year . </P> <Ul> <Li> Kickoffs that land in the end zone untouched by the receivers are blown dead and the ball put in play by the receiving team at their own 20 - yard line (touchback). </Li> <Li> Official time - outs are called for players who are "obviously injured ." Previously, teams were charged a time - out for an injured player . </Li> <Li> Fouls committed by the team not in possession of the ball behind the dead - ball spot are enforced from the dead - ball spot . </Li> <Li> Jerseys must be replaced if the numbers are no longer readable . (Tear - aways were popular for backs & receivers, later prohibited) </Li> <Li> Mouthpieces are made mandatory starting with the 1973 season . </Li> </Ul>

When did ncaa allow freshmen to play football