The expanded College Football Playoff has a decidedly old-school feel: Smothering defenses have carried the last four teams still in the hunt for the national championship.

If you want offense, look elsewhere this weekend. The defenses, with All-Americans spread throughout the lineups, are the story of the semifinals. Ohio State, Texas, Penn State and Notre Dame all rank among the top eight defenses nationally this season.

The No. 8 seed Buckeyes (12-2) meet the No. 5 Longhorns (13-2) in the Cotton Bowl on Friday night. The Buckeyes are No. 1 in total defense and scoring defense. Texas is ranked third and fourth, respectively.

The Orange Bowl matchup Thursday night between No. 7 Notre Dame (13-1) and No. 6 Penn State (13-2) feature run-stuffing defenses that shut down Georgia and Boise State's Ashton Jeanty, the nation's top running back, in the quarterfinals.

Buckeyes quarterback Will Howard, who was 0-3 against Texas when he was at Kansas State before transferring, summed up the Longhorns defense this way: “They got some dudes, man,” Howard said.

Dudes indeed. Everywhere.

Longhorns senior cornerback Jahae Barron won the Thorpe Award as the nation's top defensive back. Edge rusher Colin Simmons has a team-high nine sacks and won the Shaun Alexander Award as the nation's top freshman.

Barron leads a deep, experienced and physical secondary that has punished receivers and anchored a defense that has produced turnovers in 23 consecutive games, the longest streak in the country.

In the quarterfinal win over Arizona State, safety Michael Taaffe's late-game hit on a receiver on the final drive of regulation was reviewed for targeting before it was determined to be legal, and Andrew Mukuba sealed the victory with an interception near the goal line in the double overtime thriller that ended 39-31, the most points Texas has allowed this season.

“I think our defense has been tremendous all year,” Texas coach Steve Sarkisian said. “As far as football goes, hey, we don’t play flag football, man. This isn’t seven-on-seven. This is tackle football. We believe in playing a physical brand of football. We try to do it the right way within the rules.”

Next up for the Texas secondary is trying to corral dazzling Buckeyes freshman receiver Jeremiah Smith.

“You know, that kid can ball. He’s a big baller. Strong, strong ability. He’s a deep threat," Barron said. "He’s a physical player, and I’ll have to be physical.

Ohio State can bully opponents too, with bookend pass rushers J.T. Tuimoloau and Jack Sawyer and All-American safety Caleb Downs on the back end. The Buckeyes have allowed just 12.1 points per game, just one 300-yard passer and two 100-yard rushers all season.

When top seed Oregon beat Ohio State at midseason, Ducks quarterback Dillon Gabriel had a clean pocket all afternoon. In the Rose Bowl rematch, the No. 8-seeded Buckeyes sacked him eight times, with two each from Tuimoloau and Sawyer.

“When we’re executing and we’re at a high level, it’s hard to do anything with us,” Buckeyes defensive tackle Tyleik Williams said. “The most violent team, the team that plays the fastest, executes the most, and exceeds their game plan the most is going to win this game.”

Notre Dame and Penn State will feature their own style of violence in South Florida. Bowl. Both units rank in the top 10 in total defense and scoring defense.

After cruising past Indiana in the first round, the No. 7 seed Irish held No. 2 Georgia to 62 yards rushing and 10 points. Notre Dame forced two turnovers, and stopped the Bulldogs on all three fourth-down attempts, most notably inside the Irish 10 with just under 10 minutes left.

And they did it despite being without standout defensive tackle Rylie Mills, who was knocked out of the playoffs with a knee injury in a quarterfinals win over Indiana.

Still anchoring the Irish defense is safety Xavier Watts, a two-time AP All-American, who has six interceptions this season.

Penn State ranked fifth nationally against the run this season, allowing just 101 yards per game. In their quarterfinal win over Boise State, the Nittany Lions held Jeanty to a season-low 104 yards and forced an early fumble.

Penn State took a hit in that game when All-American defensive end Abdul Carter, the Big Ten Defensive Player of the Year, left early with an unspecified upper body injury and did not return.

Carter leads Penn State with 11 sacks and is second among all FBS players with 21 1/2 tackles for loss this season. Nittany Lions coach James Franklin seemed optimistic that Carter could return this week, even if he stopped short of saying he would.

“At this point, I don’t think there’s anything that is stopping him from playing,” Franklin said Saturday.