The Spartans won all 10 of their remaining games and finished 13-1.
Still, that single loss - and it wasn't even a bad loss - doomed them.
That's the way it was in college football for decades, a lone defeat against a good opponent often being enough to deny a team its shot at playing for the national championship. And if the old models that decided national titles were still in place today, there's almost no way Michigan State and Oklahoma would still be championship contenders.
''I think that's probably fair,'' Oklahoma coach Bob Stoops said.
Yet here they are, in College Football Playoff semifinal games on Dec. 31 and beneficiaries of a system that is more forgiving than its predecessors.
Technically, there's only been one consensus national champion - Notre Dame in 1977 - that won the title in a season where it lost to an opponent that finished with a record below .500. The Irish lost to Ole Miss that year and the Rebels finished 5-6. Ole Miss now says it went 6-5 because Mississippi State had to forfeit several wins, including one against the Rebels.
No team, at least since the advent of The Associated Press first awarding its national championship in 1936, has ever lost to someone with a 5-7 record or worse and won it all.
That might change now.
This year, Oklahoma lost to a Texas team that finished 5-7. Michigan State lost to a Nebraska team that finished 5-7. The Spartans' loss was mildly controversial because of some debatable late-game calls, but it would have obviously been difficult in the poll-only era or the Bowl Championship Series days for the Sooners or Spartans to stay in the title mix after those defeats.
The playoff committee, though, saw more than just one bad day on their resumes. That's why No. 4 Oklahoma meets No. 1 Clemson in one CFP semifinal at the Orange Bowl, and No. 3 Michigan State meets No. 2 Alabama in the other at the Cotton Bowl.
''Fact is, there's only one undefeated team and they were going to play somebody that had a loss, no matter what system was in use,'' College Football Playoff executive director Bill Hancock said. ''I think it's a good thing for the game. Every team has blemishes. Even Clemson, undefeated Clemson, had a couple. ... And these teams, after their blemishes, they turned things around and played extremely well for the rest of the season.''
Alabama lost to Ole Miss at home - prompting coach Nick Saban to now-famously say some media observers were ready to declare the Tide ''dead and buried and gone'' - but is 10-0 since. Oklahoma went 7-0 after the Texas loss, winning the Big 12 and outscoring foes by nearly five touchdowns a game. And Michigan State has won four straight, including wins over Ohio State and Iowa.
''We knew we controlled our own situation by who we were playing in the near future at that point in time,'' Michigan State coach Mark Dantonio said, referring to how the Spartans handled things after the Nebraska loss. ''So we just sort of made a statement and continued on. I think after you do have a loss or after something bad happens to you, it's how you respond to that that defines people.''
Not much was expected from Oklahoma - at least by the Sooners' lofty standards - coming into the season. They were barely a top-20 team, had to rally from 17 points down to win at Tennessee in September and then found themselves dealing with the shocking loss to rival Texas.
Who was counting Oklahoma out then?
''Everyone,'' Stoops said.
He doesn't even try to hide how much he's savoring that. And Michigan State has embraced the same way of thinking.
Sure, it can be said that the CFP committee ''put'' the Sooners and Spartans into the playoff. But those teams more than atoned for their slip-ups to earn their shots - an opportunity that wouldn't have existed in the past.
''Would I rather win them by 21 and just smile on the sideline, walk up and down? Yeah, I'd rather do that,'' Dantonio said. ''But the nature of this game is there's a lot of parity in college football, and it makes games tight, and anybody can rise up and play with anybody else. We've seen that across the board, across this country.''
AP college football site: http://collegefootball.ap.org
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