With the college football season nearing its midpoint, this weekend presents critical games in four of the six conferences with automatic BCS bids. Some were on everyone’s short-list of games of the year back in August, while others are complete surprises. Here’s a rundown:

NO. 2 TEXAS VS. OKLAHOMA AT DALLAS, SATURDAY, 1 P.M. (ABC)

Before the season, few would have guessed the Red River Rivalry would be the only one of this weekend’s big games in which one of the teams entered the game unranked. But that hardly lessens the impact for Texas (4-0), which is seeking revenge for five straight losses to Oklahoma (2-2) – several of which crippled national championship aspirations.

This year, the tables have turned – on paper at least. Oklahoma, which lost 11 players to the NFL draft and a Heisman Trophy-winning quarterback, dropped two of its first three games and is unranked, while Texas has steamrolled three of four opponents. The other win was a gutsy, come-from-behind effort at no. 6 Ohio State. The Longhorns’ performance in Columbus has many believing that this is the year Texas finally breaks the Oklahoma jinx and reaches the BCS title game, and the Longhorns certainly wouldn’t mind giving the scoreboard operator a workout in the process. But a wounded animal is a dangerous one, and Texas needs to concentrate on just beating – not blowing out – Oklahoma.

Sooners’ quarterback Rhett Bomar has been unable to generate enough out of the passing game to take the heat off banged-up tailback Adrian Peterson, who’s averaging more than a yard per carry less than he did last season, when he nearly won the Heisman as a freshman. On the other side of the ball, Oklahoma’s run defense has allowed just over 60 yards per game, and last week held the NCAA’s leading rusher, Kansas State’s Thomas Clayton, to eight yards on 12 carries.

Oklahoma will hope the defense can throw a blanket over quarterback Vince Young and the Texas rushing attack, perhaps parlaying a turnover or two into points. If the Sooners can keep the game close into the second half, the OU demons of past years are likely to creep into the minds of the Texas players, and their coach, Mack Brown. Rarely has a coach in any sport been under more pressure to win a single game than Brown is to win this one. A sixth straight loss to Oklahoma would render moot all of his success against everyone else, and would create a groundswell among Texas boosters for his dismissal.

NO. 5 GEORGIA AT NO. 8 TENNESSEE, SATURDAY, 3:30 P.M. (CBS)

Three weeks after having its season derailed against Florida, and two weeks after it returned the favor to LSU, Tennessee (3-1) plays another huge game as it hosts Georgia (4-0) in the first major test of the year for the undefeated Bulldogs.

After weeks of flip-flopping, Tennessee coach Phil Fulmer has declared Rick Clausen his starter after the senior rescued the Vols from a mess of Erik Ainge’s making against LSU. Clausen isn’t always pretty, but his experience and passing accuracy give the offense a better chance to avoid the killer mistake – which can be enough to win when paired with Tennessee’s fearsome defense.

Georgia senior quarterback D.J. Shockley has put up some decent numbers in his first year as the starter, but he has yet to face a defense anywhere close to the one he’ll see on Saturday. Tennessee’s defensive line could make it a long day for Shockley, who is unlikely to get much help from his running game against that same front four.

Tennessee can ill afford another loss if it wants to remain in SEC title contention, and if the Vols play with the desperation they showed in the second half against LSU and get some production from Clausen, they should be able to claim a home win.

NO. 10 CALIFORNIA AT NO. 20 UCL A, SATURDAY, 7:30 P.M. (TBS)

Jeff Tedford is known for developing quarterbacks – Trent Dilfer, Joey Harrington, and David Carr among them – but lately it seems as if any running back the California coach plugs into his system produces like an All-American. Marshawn Lynch was supposed to replace 2,000-yard back J.J. Arrington, but suffered an early-season injury. No matter. Justin Forsett has stepped in, and the duo has paced Cal (5-0) to nearly 260 yards a game on the ground, seventh-best in the nation.

There are questions about the level of competition, however, as Cal’s five wins have come against opponents with a combined five wins. Now the Golden Bears get their most difficult test of the season in surprising UCLA (4-0), which is out to prove that Los Angeles isn’t a one-team town. The argument took a hit last week when the Bruins were forced to come from behind to beat Washington after trailing by 10 at halftime.

UCLA has its own top ground attack with Maurice Drew and his 6.1 yards per carry. Drew will look to test the mettle of the yet unproven Cal defense. For Cal, quarterback Joseph Ayoob has looked decent in patches, but has been far too inconsistent. Tedford’s system requires downfield throws, an ability Ayoob has yet to display.

Both these teams believe they can arrive at their respective dates with USC undefeated and prove they’re more than just the second-best team in the Pac-10, but to do so, a win here is absolutely essential.

NO. 6 OHIO STATE AT NO. 16 PENN STATE, SATURDAY, 7:45 P.M. (ESPN)

The suddenly resurgent Nittany Lions host Ohio State (3-1) in an unlikely big game in the Big Ten. After four losing seasons in five years, ageless Penn State coach Joe Paterno proclaimed his program was on the verge of turning things around, but few believed him. A 4-0 start failed to raise many eyebrows – until last week’s 44-14 destruction of previously unbeaten Minnesota, in which Penn State completely shut down the Gophers’ potent running game.

Ohio State, on the other hand, has been near the top of the rankings all season, and is the best positioned one-loss team in the polls after narrowly falling to Texas. The Buckeyes also feature a dominating defense, are coming off a 31-6 decimation of Iowa, and have had a bye week to prepare for this game. Offensively, however, OSU struggles with the quarterback-by-committee of Troy Smith and Justin Zwick, both of whom have failed to get the ball into the hands of their best playmaker, receiver Ted Ginn Jr., often enough.

Penn State has done a better job of that with its all-around threat, freshman receiver Derrick Williams, who has made big plays both running and receiving. Still, this is likely to be a defensive struggle, with the winner moving to the head of the race for the Big Ten’s BCS berth and perhaps even the Rose Bowl.

Mr. Levine is a writer for FootballOutsiders.com.