Steelers center Maurkice Pouncey got treatment for his sprained left ankle while his teammates practiced Thursday for the Super Bowl.
Pouncey's availability is in question because of the injury sustained in the AFC championship.
"It's getting to be the witching hour for Maurkice," coach Mike Tomlin told a pool reporter after practice. "He's going to have to show us something very soon."
If he can't play Sunday, Doug Legursky would make his first NFL start at center.
Defensive end Aaron Smith, who has been out since Oct. 24 with a torn triceps muscle, didn't participate in scrimmages.
Ben Roethlisberger threw touchdowns on four straight red-zone series and was sharp throughout the workout. The first-team defense snagged four interceptions against scout-team quarterbacks.
"I'm glad we were sharp, but I'm not sure it really means anything for the game," Tomlin said. "I've seen us practice great on Thursday and play poorly on Sunday, and then I've seen us practice not worth anything Thursday and then come out and play great."
The Steelers worked out at TCU's indoor practice field. Horned Frogs coach Gary Patterson, several assistants and a few players watched.