BYU needs to be undefeated just to get a chance at a New Years 6 bowl. To get into the playoffs, you are going to need a lot of improbably help in addition to going 13-0.

Option 1: The teams on BYU's schedule dominate (when not playing BYU). For example: Wisconsin and LSU finish in the top 10. Utah, BSU, and Miss St finish top 20.

Option 2: At least 3 P5 conference champions have 2 or more losses (not including the SEC. I could see a 2 loss SEC champion getting tapped over BYU).

Option 3: Technically, this one is in BYU's hand, but is even less probable then the other 2. Beat LSU, Wisconsin, Miss St, Utah, and BSU all by at least 4 TDs

A 13-0 season is not impossible. Vegas has us at 10 wins. That means that the Cougars are probable favored in all games but LSU and Wisconsin. Win the games you are supposed to and pull off 2 upsets (one at home and one on a "neutral" field).

I run a simulation program. It predicts a 10-3 season, but LSU is the only game of those 3 that my simulator has BYU loosing by more than a TD.

While an undefeated season is incredibly unlikely, it is possible, and that possibility means a lot to fans.