1973 NCAA Division I football season
The 1973 NCAA Division I football season was the first for the NCAA's current three-division structure. Effective with the 1973–74 academic year, schools formerly in the NCAA "University Division" were classified as Division I (later subdivided for football only in 1978 (I-A and I-AA) and renamed in 2006 into today's Division I FBS and FCS). Schools in the former "College Division" were classified into Division II, which allowed fewer athletic scholarships than Division I, and Division III, in which athletic scholarships were prohibited.

In its inaugural season, Division I had two NCAA-recognized national champions, and they faced each other at year's end in the Sugar Bowl on New Year's Eve. The New Orleans game matched two unbeaten teams, the Alabama Crimson Tide  ranked #1 by AP and UPI, and the Notre Dame Fighting Irish  ranked #3 by AP and #4 by UPI.

While both wire services ranked Alabama first at the end of the regular season, the final AP poll was after the bowl games.  By agreement with the American Football Coaches' Association, however, UPI bestowed its championship before the postseason bowl games, and Alabama was crowned champion by UPI on December 4. UPI ranked Notre Dame fourth: one coach had given the Irish a first place vote, compared to 21 for Alabama. (In the next season, the final coaches' poll was after the bowls.)

In a game where the lead changed six times, Notre Dame won by a single point, 24–23, to claim the AP national championship.  During the 20th century, the NCAA had no playoff for major college football teams that would become 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).  In 1973, the UPI issued its final poll before the bowls, but the AP Trophy was withheld until the postseason was completed.  The AP poll in 1973 consisted of the votes of as many as 63 sportswriters and broadcasters, though not all of them voted in every poll.  UPI's voting was made by 34 coaches.  Those who cast votes would give their opinion of the ten best teams.  Under a point system of 20 points for first place, 19 for second, etc., the "overall" ranking was determined.

Conference and program changes

September
In the preseason poll released on September 3, the defending champion USC Trojans were ranked first by 55 of the 63 voters, followed by Ohio State, Texas, Nebraska and Michigan.
On September 8, #4 Nebraska beat #10 UCLA 40–13.  Most teams had not yet opened the season.  The poll was: 1.USC 2.Nebraska 3.Ohio State 4.Texas 5.Michigan
September 15: #1 USC beat Arkansas 17-0 and  #2 Nebraska and #4 Texas were idle. #3 Ohio State beat Minnesota 56-7 and #5 Michigan had beat Iowa 31-7. #6 Alabama, which beaten California 66–0 in Birmingham, rose to fourth, while Texas fell to sixth. Barry Switzer won his first game as Oklahoma head coach in a 42-14 rout of Baylor. The poll was: 1.USC 2.Nebraska 3.Ohio State 4.Alabama 5.Michigan.
On September 22, #1 USC beat Georgia Tech at Atlanta 23-6, #2 Nebraska beat #14 N.C. State 31–14, and #3 Ohio State was idle. #4 Alabama won at Kentucky, 28–14. #5 Michigan beat Stanford 47–10.  The next poll was: 1.USC 2.Nebraska 3.Ohio State 4. Michigan 5.Alabama
September 29: #1 USC was tied by #8 Oklahoma, 7–7. #2 Nebraska beat Wisconsin 20–16. #3 Ohio State beat TCU 37–3. #4 Michigan beat Navy 14–0. #5 Alabama won at Vanderbilt, 44–0.  In the next poll, the Buckeyes rose to first place: 1.Ohio State 2.Nebraska 3.Alabama 4.USC 5. Michigan

October
October 6: #1 Ohio State beat Washington State 27-3. #2 Nebraska won at Minnesota 48-7. #3 Alabama beat Georgia at home, 28-14. #4 USC won at Oregon State, 21-7. #5 Michigan beat Oregon 24-0.  The poll remained unchanged: 1.Ohio State 2.Nebraska 3.Alabama 4.USC 5. Michigan
October 13: #1 Ohio State won at Wisconsin 24-0. #2 Nebraska lost at #12 Missouri 13-12. #3 Alabama won at Florida 35-14. #4 USC beat Washington State 46-35. #5 Michigan won at Michigan State, 31-0. #6 Oklahoma beat #13 Texas 52-13 in Dallas #7 Penn State beat visiting Army, 54-3, to extend its record to 5-0-0 and rise to the top five.  The poll:  1.Ohio State 2.Alabama 3.Oklahoma 4.Michigan 5.Penn State
October 20: #1 Ohio State won at Indiana 37-7. #2 Alabama beat #10 Tennessee at Birmingham, 42-21. #3 Oklahoma beat #16 Colorado 34-7. #4 Michigan beat Wisconsin 35-6. #5 Penn State won at Syracuse 49-6.  The poll was unchanged: 1.Ohio State 2.Alabama 3.Oklahoma 4.Michigan 5.Penn State
October 27: #1 Ohio State beat Northwestern 60-0. #2 Alabama crushed Virginia Tech at home, 77-6. #3 Oklahoma won at Kansas State 56-14. #4 Michigan won at Minnesota 31-0. #5 Penn State crushed West Virginia 62-14. #8 Notre Dame rose to fifth after its 23-14 win over USC.  The poll was 1.Ohio State 2.Alabama 3.Oklahoma 4.Michigan 5.Notre Dame

November
November 3: #1 Ohio State won at Illinois 30-0. #2 Alabama beat Mississippi State in Jackson, 35-0. #3 Oklahoma beat Iowa State 34-17. #4 Michigan beat Indiana 49-13. #5 Notre Dame beat Navy 44-7.  The poll was unchanged: 1.Ohio State 2.Alabama 3.Oklahoma 4.Michigan 5.Notre Dame
November 10: #1 Ohio State recorded its 3rd shutout, a 35-0 win over visiting Michigan State. #2 Alabama was idle. #3 Oklahoma won at #10 Missouri 31-3. #4 Michigan beat Illinois 21-6. #5 Notre Dame won at #20 Pittsburgh 31-10.  The poll: 1.Ohio State 2.Alabama 3.Oklahoma 4.Michigan 5.Notre Dame
November 17: #1 Ohio State beat Iowa 55-13. #2 Alabama beat Miami (Florida) at home, 43-13. #3 Oklahoma  beat #18 Kansas 48-20. #4 Michigan won at Purdue, 34-9. #5 Notre Dame was idle.  The poll: 1.Ohio State 2.Alabama 3.Oklahoma 4.Michigan 5.Notre Dame
On Thanksgiving Day, #2 Alabama beat #7 LSU 21-7 and #5 Notre Dame beat Air Force 48-15.  The next day, #3 Oklahoma beat #10 Nebraska 27-0.
The big matchup was on Saturday, November 24, in Ann Arbor, Michigan, where #1 Ohio State (9-0-0) and #4 Michigan (10-0-0) met.  The two teams played to a 10-10 tie. The next day, Big Ten Conference athletic directors voted to send Ohio State to the Rose Bowl, due in large part to the broken clavicle suffered by Michigan quarterback Dennis Franklin in the game. Alabama, still unbeaten and untied, took over the top spot in the next poll:  1.Alabama 2.Oklahoma 3.Ohio State 4.Michigan 5.Notre Dame

December

December 1: The top six teams were unbeaten. #1 Alabama shut out Auburn in Birmingham 35-0, avenging Auburn's shocking upset in the previous year, to close the regular season with an 11-0-0 record. #2 Oklahoma won at Oklahoma State 45-18 to conclude their season with a 10-0-1 record. #5 Notre Dame won at Miami (Florida) 44-0. 

Elsewhere, Bluebonnet Bowl-bound Tulane defeated Orange Bowl-bound LSU 14-0 to end a 25-year winless drought in the Battle for the Rag in the final meeting at Tulane Stadium, leaving both the Green Wave and Bayou Bengals 9-2. Also, the 4-7 Navy Midshipmen trounced the Army Cadets 51-0. As for the Cadets, they completed one of their worst season in their football program history, when they completed a season with an imperfect 0-10 record.

In the final regular season poll, the top six schools were unbeaten.  1.Alabama (11-0) 2. 2.Notre Dame (10-0) 3.Oklahoma (10-0-1) 4.Ohio State (9-0-1) 5.Michigan (10-0-1) and 6.Penn State (11-0).  The other major college unbeaten, Miami (Ohio) (10-0-0), was #15.  Oklahoma, however, was on probation for having used an ineligible player (Kerry Jackson) in three 1972 games, and was ineligible to play in a bowl game.  #1 Alabama and #2 Notre Dame accepted invitations to play in the Sugar Bowl.

Rule changes
Each team may use its own legal ball when it is in possession. 
Free substitution is allowed, however substitutes both checking in and leaving the field of play must do so through their own team areas, and are not required to stay in or leave for one play.  This change would be rescinded in the 1974 season.
The fair catch signal is standardized as waving one arm side to side before the ball is caught.  Any other signal (including shielding of the eyes) is considered invalid, and players making a fair catch with either a valid or invalid signal are protected from being tackled or blocked.  Previously, receivers making an invalid signal were not afforded any protection.
All players are required to wear a mouth guard and a fully buckled chin strap.  Violators must leave the field until the violation is corrected.
If an illegal forward pass is completed in the end zone (whether to an eligible or ineligible receiver), the ball is dead and the penalty enforced.

Conference standings

Bowl games

Major bowls
Monday, December 31, 1973
Tuesday, January 1, 1974

Alabama and Notre Dame had never met in a college football game before their encounter in the Sugar Bowl, which was played on New Year's Eve at Tulane Stadium, with kickoff at 7:15 pm CST. Two legendary coaches, Bear Bryant and Ara Parseghian brought their teams to New Orleans, and the game was a thriller.  The Irish scored first, but missed the extra point.  After Alabama took a 7–6 lead, freshman Al Hunter returned the ensuing kickoff 93 yards for a touchdown, and a two-point conversion put Notre Dame up 14–7.  Alabama went ahead 17–14 in the third, but a fumble on their own 12-yard line gave the Irish a chance to make it 21–17.  In the fourth quarter, Bama got back the lead on a trick play, as quarterback Richard Todd handed off to running back, Mike Stock, who then fired a touchdown pass back to Todd; but Bill Davis, who had made 51 of 53 extra point attempts in his career, was wide right, and the score stayed 23–21.  In the final minutes, Notre Dame's Bob Thomas (who had missed the earlier point after try) kicked a 19-yard field goal that gave the team the 24–23 win. Asked whether Notre Dame would be voted #1, Coach Parseghian replied, "Certainly.  What was the final score?"

The final AP writers' poll was split.  Notre Dame received a majority of the first place votes, 33 out of 60, followed by #2 Ohio State (11 votes) and #3 Oklahoma (16 votes, but fewer points overall).  The fourth spot (held by Notre Dame in the final UPI poll) went to Alabama. UPI, who crowned Alabama as national champion at the end of the regular season, would begin holding the coaches' poll after the bowl games beginning with the 1974 season.

Other bowls

 Prior to the 1975 season, the Big Ten and Pac-8 conferences allowed only one postseason participant each, for the Rose Bowl.

Heisman Trophy
Running back John Cappelletti had the third best year in Penn State  history when he gained 1,117 yards rushing in 1972. As a senior in 1973, he had the second best year in school history rushing for 1,522 yards. In his two-year running career, he gained 100 yards in the thirteen games and had a career total of 2,639 yards and twenty-nine touchdowns for an average of 120 yards per game and 5.1 yards per carry. Cappelletti's acceptance speech on December 13 at the Heisman Dinner (with new Vice President Gerald Ford next to him on the dais) was considered the most moving ever given at these ceremonies, as he honored his 11-year-old brother Joey, a victim 

John Cappelletti, RB - Penn State, 1,057 votes
John Hicks, OT - Ohio State, 524 
Roosevelt Leaks, RB - Texas, 483 
David Jaynes, QB - Kansas, 394 
Archie Griffin, RB - Ohio State, 326
Randy Gradishar, LB - Ohio State, 282 
Lucious Selmon, NG - Oklahoma, 250 
Woody Green, RB - Arizona State, 247 
Danny White, QB - Arizona State, 166 
Kermit Johnson, RB - UCLA, 122 
Tony Dorsett, RB - Pittsburgh, 118 
Lynn Swann, SE - USC, 108 
Anthony Davis, RB - USC, 104
Condredge Holloway, QB - Tennessee, 98 
 Leaks, Davis, and Holloway were juniors, Griffin a sophomore, Dorsett a freshman
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