Three undefeated teams went down last week, and this week has the potential for more fireworks. Here are some of the big questions going into Saturday:

Can Baker Mayfield Lead the Sooners to an Upset?

The Big 12’s month of reckoning is finally upon us, with Baylor, TCU, Oklahoma and Oklahoma State all taking part in what is essentially a round-robin tournament for the conference title. While most observers think an undefeated Big 12 champion would jump into the playoffs, No. 12 Oklahoma could throw a wrench into the works this week with an upset of No. 6 Baylor.

One of this season’s unlikeliest heroes is Sooner quarterback Baker Mayfield. The Texas Tech transfer walked on at Oklahoma right after Trevor Knight’s performance for the ages in the 2014 Sugar Bowl. Not only did Mayfield beat Knight out for the starting job this year, but he has the Sooners back in the national title mix. Mayfield has the Sooners peaking at the right time: they have scored 50-plus points in four straight games for the first time since 2008. He ranks second nationally in passer efficiency and sixth in touchdown passes. Since the Sooner’s early-October loss to Texas, the junior has completed nearly 76 percent of his passes for 1,219 yards, 14 touchdowns and just one interception.

Baylor has beaten the Sooners by a combined 63 points the last two seasons, and winning in Waco will be no easy task. But if Mayfield can lead Oklahoma to an upset win this weekend, he will not only have the Sooners back in title contention -- he could rocket himself into the Heisman discussion.

Can Alabama Keep Rolling?

Despite an early-season loss to Ole Miss, No. 2 Alabama is right where it wants to be: controlling its own destiny in the SEC and securely in the playoff mix. The Crimson Tide know that, if they win out, they'll have a chance to play for their fourth national championship in seven years.

After corralling Leonard Fournette last week, Alabama will now look to contain Mississippi State quarterback Dak Prescott, who has thrown for 998 yards and 10 touchdowns in his last three games. He has thrown just one interception this season, but will face his toughest test to date against a Crimson Tide defense that ranks 13th nationally in interceptions and third in total defense. Alabama picked off Prescott three times in last year's 25-20 win when Mississippi State came in ranked No. 1.

Can Oklahoma State Exorcise Their Demons in Ames?

Four years ago, a trip to Iowa State doomed Oklahoma State's national title hopes. Now the No. 8 Cowboys are looking to make sure that doesn't happen this year as Mike Gundy's undefeated crew, fresh off a big upset of TCU, is squarely in the title conversation.

OSU quarterback Mason Rudolph, who threw for 352 yards and five scores against the Horned Frogs, will look for another big game against a Cyclone defense that ranks 109th nationally in pass defense. The Cowboys are certainly the better team in this game and, if they win out, should be in the playoffs. Winning in Ames, though, is certainly no given.

Who Leads the Heisman Race?

One week ago, it seemed like a foregone conclusion that LSU running back Leonard Fournette was going to run away with the Heisman Trophy, with TCU quarterback Trevone Boykin maybe finishing a distant second. But just a few days later the whole race is up for grabs again, as both front-runners fell flat on the big stage.

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After rushing for 150-plus yards in every game this season, Fournette garnered just 31 yards on 19 carries against Alabama. Boykin, meanwhile, threw four picks and just one touchdown in the loss at Oklahoma State.

To be sure, Fournette (who leads the nation in rushing) and Boykin (third nationally in passing) are still very much in the mix. But the race is now wide open with big-name players like Alabama running back Derrick Henry (leads the nation in rushing touchdowns; tallied 589 yards and seven scores in his last three games), Baylor receiver Corey Coleman (first nationally in receiving yards per game and touchdowns) and Stanford back Christian McCaffrey (leads the nation in all-purpose yards) now in the discussion.

Can Stanford Punch Its Playoff Ticket?

In the last five years, the winner of the Oregon/Stanford match-up has gone on to win the Pac-12. But No. 7 Stanford knows that if they can keep rolling, the stakes will be even higher with a possible playoff spot on the line. Stanford must get past Oregon and California the next two weeks to set up a possible playoff play-in game with No. 4 Notre Dame on November 28.

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Cardinal running back Christian McCaffrey leads the nation in all-purpose yards per game (241.6) and is on pace to become the Pac-12's fifth player since 1978 to average 200-plus per game. But it should be a fun contest to watch between McCaffrey and Oregon's Royce Freeman, who leads the conference in rushing.

While this hasn't been a vintage season for the post-Marcus Mariota Ducks, Oregon (6–3) has won three straight and rolled up a school-record 777 total yards in last week's win over California. The Ducks might be out of contention for a Pac-12 title or a major bowl game, but ending their rival's playoff hopes would be a nice consolation prize.