FORT WORTH, Texas -- — TCU quarterback Max Duggan outran the Oklahoma defense for a long touchdown and lofted passes to wide-open receivers for other lengthy scores.

Oklahoma's Dillon Gabriel never got much of a chance to match him.

Duggan went 67 yards for one of his two rushing TDs and threw for three scores, leading the Horned Frogs to a 55-24 rout of the 18th-ranked Sooners on Saturday in a second consecutive loss for first-year coach Brent Venables.

"We're not very good obviously right now," Venables said. "We've got a lot to get better at. We've got to give them answers and we've got to help get them better quickly."

Gabriel was knocked out of the game in the second quarter when he was hit in the head while sliding by TCU linebacker Jamoi Hodge, who was ejected for targeting.

Players had to be separated after Hodge's hit while Gabriel stayed down for several minutes, surrounded by the medical staff, before the Central Florida transfer walked off the field on his own.

Gabriel remained on the sideline without his helmet, and Venables said after the game his quarterback was being evaluated for a concussion. Pittsburgh transfer Davis Beville replaced Gabriel and struggled.

There was an even longer delay in the fourth quarter when Oklahoma defensive back Damond Harmon was carted off after being immobilized on a stretcher. Harmon flashed a thumbs-up as he was put on the cart in an emotional scene that included Oklahoma linebacker Kelvin Gilliam, a childhood friend and high school teammate, appearing to fight back tears.

Venables said a surgeon on site believed Harmon's neck was stable, and a precautionary MRI was planned. The coach said Harmon had a history of back issues.

When Lincoln Riley shocked the Sooners by leaving for Southern California, they hired their former defensive coordinator after Venables won two national titles in that role at Clemson.

His defense was no match for Duggan and company as Oklahoma lost consecutive regular-season games for just the second time since 1999. The Sooners (3-2, 0-2 Big 12) opened conference with a home loss to Kansas State.

"We're just not playing with great cohesion right now," Venables said. "Giving up big plays on defense and turning the ball over, or just not being efficient on offense, are recipes for disaster."

It's the most points Oklahoma has allowed since a 63-28 loss to LSU in the 2019 national semifinals. The Horned Frogs (4-0, 1-0) had four touchdowns of at least 62 yards, topped by Taye Barber's 73-yard catch during a 27-point first quarter.

TCU led 41-17 at halftime with 479 yards while finishing with 668 yards in coach Sonny Dykes' Big 12 debut after four seasons at crosstown rival SMU.

Kendre Miller ran 69 yards for a touchdown to put TCU up 48-17 early in the second half and finished with 136 yards and two touchdowns on 13 carries. The active FBS career leader in yards per carry increased his mark by averaging 10.5 yards.

"Had a bunch of big plays on offense," Dykes said. "That's the formula for us right now is if we can make big plays and take care of the ball, then good things are going to happen for us."

Duggan took off to the right and beat everyone to the sideline on the long score, then added a 35-yard run before capping the final TD drive with a 2-yard run, finishing his day in the third quarter.

"I don't think really (it's about) the way we won, it's just that we won," said Duggan, who had 302 yards passing and 116 rushing said. "It doesn't matter how much you win by, how it looks. You get the win, that's a big deal, especially in this league."

Both teams had committed just one turnover apiece coming in, but Oklahoma opened with a mistake that would be a sign of things to come. The Sooners won the toss and decided to take the ball instead of deferring, but receiver Marvin Mims fumbled on the third play of the game. TCU took advantage and opened the scoring when Duggan's 19-yard scoring pass to Savion Williams finished a 46-yard drive.

When the Sooners weren't being penalized for defensive pass interference (three times in the first quarter), they were leaving receivers wide open in the secondary. Taye was alone on his long TD, as was Gunnar Henderson on a 62-yard score.

Jovantae Barnes had 100 yards rushing and two touchdowns for the Sooners.

THE TAKEAWAY

Oklahoma: This is the second time in three seasons the Sooners have started 0-2 in the Big 12. They rallied to win the league in the pandemic-shortened 2020 season, but were never manhandled like this.

TCU: The Horned Frogs averaged 10.2 yards per play while building their big halftime lead and finished at 8.9 after coming in second nationally at 8.1 yards per play.

POLL IMPLICATIONS

Oklahoma's 31-week streak of being in the Top 25 is in jeopardy, while TCU has a good chance to get in for the first time since a one-week showing at 25th early in the 2019 season.