SOUTH BEND, IN – SEPTEMBER 05: The Notre Dame Fighting Irish Leprechaun celebrates a touchdown against the Texas Longhorns during the first quarter at Notre Dame Stadium on September 5, 2015 in South Bend, Indiana. (Photo by Jon Durr/Getty Images)The initial College Football Playoff rankings came out this past Tuesday, and Notre Dame fans were likely happy with what they saw – coming in at No. 4. But there’s a nightmare scenario brewing for the Fighting Irish, potentially.Each year, FiveThirtyEight puts out a College Football Playoff predictor that allows users to plug in different scenarios for the final few weeks of the season. Notre Dame fans won’t like one specific scenario – which could happen.If you assume that Alabama, Clemson, Notre Dame, Oklahoma and Ohio State are all going to win out, FiveThirtyEight gives the Fighting Irish the lowest chances of getting into the Playoff.In such a scenario, Alabama and Clemson would have over 99-percent chance of getting in. Ohio State would be at 72-percent, with Oklahoma at 65-percent. Notre Dame would be 60-percent.Oklahoma lost to Texas, while Ohio State lost to Purdue. So they’d be getting in over an undefeated Notre Dame team.Why would this happen? It’s hard to pinpoint, but both Oklahoma and Ohio State will have conference title games to make their cases. Notre Dame, being independent, would not.This probably won’t happen, but if it does, there will be a lot of pressure on Notre Dame to reconsider joining a conference. There will also be a ton of college football fans calling for an expanded playoff.