Ultimate Playoff: Final Four

No. 1 Ohio State vs. No. 4 Oklahoma: In the offseason, both teams lost key contributors in the backfield (Troy Smith and Antonio Pittman for Ohio State, Paul Thompson and Adrian Peterson for Oklahoma), leaving some major voids to fill. But both offenses have transitioned almost seamlessly to a new group of big-time performers. Todd Boeckman has admirably replaced Smith -- the 2006 Heisman Trophy winner. The 23-year-old junior leads the Big Ten in passing efficiency and threw at least two touchdown passes in Ohio State's first 10 games. Even though he's battled injuries for much of the season, RB Chris "Beanie" Wells has been spectacular in his first year as a starter. Averaging 5.8 yards per carry, Wells has accumulated 1,463 yards and 14 touchdowns, including 222 yards and two scores against archrival Michigan. For the Sooners, redshirt freshman QB Sam Bradford has been one of the most surprising stars of 2007. Bradford, who won his job in fall practice, leads the nation in passing efficiency, having thrown a freshman-record 34 touchdown passes to just seven interceptions. At running back, OU has featured a three-headed monster consisting of Allen Patrick, DeMarco Murray and Chris Brown. Patrick is the most well-rounded of the bunch, while Brown excels on the goal line and Murray provides a home run threat. Murray is out for the season with a knee injury, but Patrick and Brown could give Ohio State some trouble.

Year in and year out, these two teams possess formidable defenses, and this season's no different. The Buckeyes rank first in total defense and scoring defense (yielding just 10.7 points per game). Ohio State is loaded at every position, boasting a number of NFL-caliber stars (including Vernon Gholston, James Laurinaitis and Malcolm Jenkins). The Sooners stingy defense gives up just 18.15 points per game. Big 12 Defensive Player of the Year Curtis Lofton has racked up 132 tackles, two interceptions, four forced fumbles and a fumble recovery.

No. 7 USC vs. No. 11 Florida: In a recent interview with Tim Tebow, SI.com's Gene Menez asked the 2007 Heisman Trophy winner which team he would most like to play. Tebow's answer: USC. Well, Timmy, ask and you shall receive. Tebow and the explosive Gators' offense face quite possibly their toughest challenge of the season in USC's vaunted defense. Yes, Florida did play LSU, but the Trojans rank better than the Tigers in most defensive categories. Each level of USC's defense features frightening talent. Up front, the Trojans have Pac-10 Defensive Player of the Year Sedrick Ellis and speedy defensive end Lawrence Jackson. Keith Rivers and Rey Maualuga headline one of the nation's finest linebacking units. And the secondary is chock-full of future pros, including FS Taylor Mays, SS Kevin Ellison and CB Terrell Thomas. Can Tebow, Percy Harvin, Andre "Bubba" Caldwell and Cornelius Ingram crack this near-impenetrable defense?

The Trojans' offense has been inconsistent all season. Granted USC has dealt with a number of injuries, but the Trojans rank uncharacteristically low in total offense (41st). Quarterback John David Booty has struggled to jell with his young receiving corps, but he should be able to take advantage of a suspect Florida secondary. The key matchup in this game could be Trojans tight end Fred Davis versus Gators LB Brandon Spikes. Davis is one of the most imposing pass-catchers in America, but Spikes has been rock-solid in coverage all season.

• No. 1 Ohio State defeats No. 9 West Virginia: 82,035 (53 percent) to 73,390 (47 percent).

• No. 4 Oklahoma defeats No. 5 Georgia: 92,995 (53 percent) to 82,041 (47 percent).

• No. 7 USC upsets No. 2 LSU: 123,982 (55 percent) to 101,200 (45 percent).

• No. 11 Florida upsets No. 3 Virginia Tech: 125,479 (68 percent) to 58,363 (32 percent).

• No. 1 Ohio State defeats No. 16 Tennessee: 136,283 (74 percent) to 47,751 (26 percent).

• No. 2 LSU defeats No. 15 Clemson: 178,183 (93 percent) to 13,402 (seven percent).

• No. 3 Virginia Tech defeats No. 14 Illinois: 129,160 (65 percent) to 70,678 (35 percent).

• No. 4 Oklahoma defeats No. 13 Boston College: 174,327 (87 percent) to 27,819 (13 percent).

• No. 5 Georgia defeats No. 12 Arizona State: 145,082 (84 percent) to 27,819 (16 percent).

• No 11 Florida upsets No. 6 Missouri: 130,996 (70 percent) to 56,304 (30 percent).

• No. 7 USC defeats No. 10 Hawaii: 140,157 (74 percent) to 50,217 (26 percent).

• No. 9 West Virginia upsets No. 8 Kansas: 126,413 (68 percent) to 60,283 (32 percent).