1. Joe Burrow misses time
This is an easy entry for No. 1. If Joe Burrow goes down and has to miss an extended period of time, the Bengals aren't the same team. It's that simple.
As unfair as it is that one player has this much power over a team, that's how it works in the NFL for teams with a franchise quarterback. It's good when the guy is healthy and doing what he does best but if something happens to him and you're forced to rely on the backup, that's when it sucks.
While the Bengals were wise not to roll with Brandon Allen as their backup again and upgraded to Trevor Siemian, let's not get it twisted here. If Burrow has to miss more than a handful of games, Siemian isn't taking this team to a Super Bowl.
The Bengals have been fortunate that Burrow has been able to remain relatively healthy since his season-ending injury in his rookie year but injuries can strike at any time. If Burrow does get banged up and has to miss a significant amount of time, it would be catastrophic for the Cincinnati Bengals and their Super Bowl chances.