The LSU Tigers were 13-0 until being humbled by Alabama in last season’s BCS championship game. They enter this season ranked No. 1 in several polls, including the USA Today coaches poll. So their only possible best-case scenario entails hoisting a Waterford Crystal football.

But what will it take to reach that goal? And how many losses would constitute a disastrous season?

Here are scenarios that could unfold in 2012:

Best-case scenario: The Tigers ease into the season with home games against North Texas, Washington and Idaho -- new quarterback Zach Mettenberger should be able to exploit defenses before LSU goes to Auburn on Sept. 22. With Mettenberger comfortable as a starter and keeping defenses honest with his strong arm, the running game should be even more dominant. The Tigers return four backs who ran for 2,338 yards and 30 touchdowns last season.

Defensively, a front featuring ends Sam Montgomery and Barkevious Mingo and tackle Bennie Logan takes pressure off a secondary missing Tyrann Mathieu. The most talented team in the nation plays like it, beating Alabama on Nov. 3 in Death Valley. (LSU is currently favored by 2.5 or 3 points.) The Tigers go on to win at Arkansas on Nov. 23 and dispatch Georgia again in the SEC title game. Then they harass USC’s Matt Barkley into a miserable final college game to finish 14-0.

Worst-case scenario: Mettenberger’s inexperience shows with some costly interceptions. The Tigers don’t get the game-changing plays Mathieu (15 turnovers caused in 26 career games) produced routinely. Opponents, staying away from corner Tharold Simon, pick on and burn whichever freshman replaces Mathieu. Even in that doomsday scenario, the Tigers should go no worse than 9-3, the losses coming to South Carolina, Alabama and Arkansas. Counting a bowl win, that’s a 10-3 season most teams would welcome. But for an LSU squad featuring four potential first-round NFL picks on defense -- Montgomery, Mingo, Logan and safety Eric Reid – it would be a huge letdown.

For more up-to-the-minute news and analysis from SEC bloggers Daniel Lewis and Larry Hartstein, follow @CBSSportsSEC.