College Football Playoff race: What the contenders need to make the top four

Purdue shakes up playoff picture with upset of No. 2 Iowa (2:26)

Spencer Petras throws four interceptions as the second-ranked Hawkeyes lose to Purdue 24-7. (2:26)

The Big Ten's chances of having two teams finish in the top four took a serious nosedive Saturday when Iowa lost at home to unranked Purdue. In the ideal scenario for the Big Ten, the selection committee would have considered both the conference champion and its one-loss runner-up, had Iowa managed to finish the regular season undefeated before losing a close game in the Big Ten title game.

Now, unless Iowa wins the Big Ten (which would ultimately be more surprising than its loss Saturday), the conference needs to bank on the East champion emerging as its lone representative.

In spite of their No. 2 ranking heading into the weekend, the Hawkeyes no longer look like a serious contender -- but it's still too early to eliminate them. The same can be said for fellow one-loss teams Oregon, Penn State, Ohio State and Alabama.

Some teams have a far more difficult path to the playoff, while others -- like undefeated Cincinnati -- might not need as much help as you think. For now, Georgia is the outlier to the chaos. The Bulldogs have separated themselves as a clear No. 1 and avoided any sense of an upset Saturday against Kentucky. Assuming they run the table and win the East, Georgia can potentially lose the SEC title game to Alabama and still finish in the top four.

Everyone else? They need a few things to go their way.

Here's a breakdown of what some top contenders -- and a few sleeper candidates -- need in the second half of the season to be considered on Selection Day:

Ohio State

What the Buckeyes need: Run the table and win the Big Ten. It's pretty straightforward. The loss to Oregon can be overcome easily with wins against Penn State, Michigan State, Michigan and a conference title. That résumé would trump anything Cincinnati, and the Big 12 and ACC champs, would finish with. Even if Alabama and Georgia both finish in the top four, the Buckeyes likely would join them in this scenario.