Oklahoma quarterback Dillon Gabriel is in concussion protocol after leaving Saturday's 55-24 loss to TCU following a blow to the head on a slide in the second quarter.
Gabriel did not return as the Sooners dropped their second consecutive game.
With Oklahoma trailing 34-10, Gabriel ran around the left end, slid feet-first and was hit hard by TCU linebacker Jamoi Hodge, who lowered a shoulder into Gabriel's helmet. Gabriel laid on the turf for several minutes as players on both teams had to be separated.
Hodge was flagged for targeting and ejected.
"I don't think a whole lot about the hit," Oklahoma coach Brent Venables said after the game, while saying he had no further update yet. "It's football ... it's part of the game. My concern is with Dillon and his health and his safety."
The Sooners suffered another scary injury in the fourth quarter when defensive back Damond Harmon laid on the turf after being knocked back while making a tackle in the fourth quarter.
Both teams kneeled on the field as medical staff put Harmon on a stretcher and took him for further evaluation.
"He's had a history of some back issues," Venables said. "A surgeon that was there felt like his neck was stable and OK, but they're going to do an MRI, check him out and take obviously some precautions. He was in some pain, an awful lot of pain."
TCU coach Sonny Dykes led off his postgame news conference by saying he hoped Harmon was OK and that his thoughts go out to him, also saying he regretted the injury to Gabriel.
"I hated the way that played out," Dykes said. "Dillon is such a good player. And I know Jamoi certainly didn't intend for that to happen. He was upset about it. My thoughts are with those guys and I hope they're both back quickly and playing for Oklahoma."
Gabriel, who was 7 of 16 for 12 yards before the injury, walked off the field with help and was later ruled out for the rest of the game. Gabriel was replaced by Davis Beville, a 6-foot-6, 235-pound junior who transferred from Pitt this offseason.
Beville finished 7 of 16 for 50 yards.