The 6-foot-3, 310-pound Killings, playing special teams, hit Hall on a block as Jerome Mathis was returning a kickoff in the second quarter. The Texans said Killings suffered a neck injury, but had feeling in his extremities.
"It's a scary part of football," said Houston coach Gary Kubiak. "Cedric is a great kid and we're just going to cross our fingers and say some prayers and hope everything is going to be all right."
Hall and Killings went down together and Hall walked slowly off the field with trainers helping him. Colts coach Tony Dungy said Hall suffered a shoulder injury.
Killings lay motionless as trainers attended to him and a stretcher was wheeled onto the field. Kubiak watched medical personnel strap Killings to the stretcher as players from both sides waited intently.
Kubiak said Killings has a deep cut under his right eye. He was moving his arms and legs and speaking as he was being treated on the field, Kubiak said.
"Initially, he made a couple of comments that he couldn't feel down low," Kubiak said. "As he laid there and talked to us, he did move everything. He talked to me. His teammates called out to him from a distance and they don't know it, but he was respondent to them."
The 30-year-old Killings was cut by the Texans on Sept. 1, then re-signed on Sept. 14 to add depth to the defensive line when Travis Johnson injured his ankle.
"We all come out on this field and our intentions are to walk off the field at the end of the game," said Houston cornerback Dunta Robinson. "For him to be carried out on a stretcher, it was a scary situation."
In the season opener, the Buffalo Bills lost tight end Kevin Everett to a life-threatening spinal cord injury. Everett, however, is making a strong recovery and doctors expect he'll be able to walk again.
"You pray for these guys to recover," said Colts quarterback Peyton Manning. "You don't wish that on anybody."
Early in the second quarter Sunday, Houston running back Ahman Green left the game with a left knee sprain.
Green, Houston's leading rusher, caught a short pass and was tackled after a 9-yard gain by Colts safety Bob Sanders. Green hopped up, but limped off the field as trainers attended to him on the sideline.