Until the 2020 season it was impossible for an NFL team to go 20-0. But as of 2020 it is possible!
This is because starting with the 2020-21 season the playoffs have been exapnded by 2 teams to 14 teams, and so as a result the second seed in each conference doesn't get a bye week during the wild card weekend anymore.
The NFL schedule hasn't changed, and teams will still play 16 weeks (for now) as follows:
- Case 1: 6 games against divisional rivals: 3 at home, 3 away
- Case 2: 4 games against teams on another division in the same conference
- Case 3: 4 games against teams on another division in the other conference
- Case 4: 2 games against the other two teams in the same conference that finished on the same spot within their respective division (that is all teams that finished 3rd in their divisions in NFC last season not covered by case 2 will plays each other this season)
This allows for 2 teams per conference to go undefeated during the regular season. We'll see how next.
Without loss of generality, let's label the 4 divisions in each conference A, B, C, and D. It's possible for the 4 cases above to happen as follows:
- Case 1: Each team plays divisional rivals
- Case 2: Teams in division A play against team in division B in the same conference. Same for divisions C & D
- Case 3: Teams in division A play against teams in division B in the other conference. Same for division C & D
So far we can see that top teams in divisions A & C haven't played each other and can both be undefeated
- Case 4: Top Seeds in divisions A & C beat 2 other teams that have already been defeated
Hence top seeds of divisions A & C in BOTH conferences now have 16-0 record. So far nothing has changed since before the 2020 season. Image below visualizes the above schedule with cases 2 and 3 marked on it. Divisions A & C are displayed in red as they have undefeated champions.
Let's denote winners of division A and C as Aw and Cw respectively, and assume Aw owns the tie break over Cw. So on the wild card weekend, Cw plays the bottom wild card while Aw has a bye. Note that Cw didn't have to play a game on wild card weekend before the 2020 season. With a win, Cw earns an extra win compared to Aw.
Both Aw and Cw win their next games, and meet in the conference finals. Aw has a record of 17-0 and Cw 18-0. Consider the case both Cw teams win their conferences. Now two 19-0 teams face off in the Super Bowl, leaving a 20-0 team as the Super Bowl champions.