Derrick Thomas underwent more than four hours of surgery today to rebuild part of his spine, and doctors said his spinal cord was not damaged as badly as feared.

Thomas's spinal cord was severely bruised, neurosurgeon Barth Green said.

Doctors originally thought it might have been severed when Thomas, 33, was thrown from his car Sunday after losing control on an icy highway near Kansas City, Mo. Thomas broke his spine and neck and wound up semiconscious with no feeling in his legs.

Though the NFL star remained paralyzed from the chest down at Jackson Memorial Hospital, doctors expressed hope he would walk again.

"There have been cases of people with similar injuries who have recovered, and there have been people who haven't recovered," Green said. "Anybody who knows Derrick knows that you don't bet against him. But it's too early to tell right now. We just have to see how he does."

The Kansas City Chiefs linebacker's operation included decompressing the spinal cord, stabilizing the spinal column with screws, titanium rods and hooks and implanting bone grafts from Thomas's hip.

Doctors said surgery went as planned, and Thomas, who remained sedated this afternoon, could be transferred to a rehabilitation facility in about two weeks.

He has begun working with therapists.

In the meantime, he will be surrounded with family and friends. His mother, Edith Morgan, and other relatives were at the hospital along with teammate James Hasty and former teammate Neil Smith.

"Derrick is in very good spirits, he's got his usual sense of humor, and he's taking all of this one day at a time," Morgan said. "One of the first things he said to me was, 'Mom, I'm going to have to have a lot of rehab.' But he's real positive and real optimistic about everything.

"We know that we have a long road ahead of us, but we're going to get through this."

The hospital is the home of the Miami Project to Cure Paralysis, the world's largest spinal cord injury research center, and its surgeons have operated on several famous athletes, including race car driver Emerson Fittipaldi.

Mike Tellis, one of Thomas's two passengers in the car, was killed as they were en route to Kansas City International Airport for a trip to the NFC championship game in St. Louis. Thomas's car flipped several times.

Thomas and Tellis, 49, of Kansas City, Kan., were not wearing seat belts and were thrown from the car, police said. Tellis was killed instantly. A third man in the car who was wearing a seat belt was treated and released.

Thomas holds the NFL one-game record of seven sacks.

"Derrick has a chore ahead of him, but knowing Derrick he will get it done," Chiefs President Carl Peterson said. "But it's going to take some time."