Dr. Walter Lowe said Williams is expected to walk again after surgery Sunday in Dallas to fuse and stabilize the cervical spine levels C-2 through C-4, but the severity of the injury makes it "highly unlikely that Harry will return to football."
The 26-year-old Williams was hurt in a collision with a teammate while trying to make a tackle on a kick return in the first quarter of Friday's game.
"The bottom line from my perspective is the surgery went well," Texans coach Gary Kubiak said Monday. "Right now it's a rough day for him but everything went well."
A third-year pro who spent last season on the Texans practice squad, Williams had fought his way into the receiver picture this season. Kubiak said last week that Williams was the team's best special teams player.
"It's hard. In this business you root for kids," Kubiak said. "He was fixing to be a big part of this team and to go out there on that field and see this kid laying there after what he went through was tough."
"Words can't explain how I feel," fellow receiver Andre Johnson said. "We were talking about it this morning. You can be out there in one play and it can be over for you, just like that."
Williams is the second player in the past year the Texans have lost to a spinal injury. Defensive tackle Cedric Killings was injured in a headfirst collision with Indianapolis receiver Roy Hall in September, fracturing the C-4 vertebra.
"I talked to Cedric the other day and he told me how well he's doing," Kubiak said.
Like Williams, Killings initially couldn't move his hands or feet. But after surgery he recovered well enough to walk into practice later in the season.
Johnson looks forward to that day with Williams.
"We're rooting for him, and I just can't wait to see him walk through those [practice] gates," he said.
The Texans signed fullback Jon Abbate on Sunday to take Williams' roster spot.
RB Ahman Green, who is nursing an injured groin, worked out on Monday. Green is expected to be ready for the regular season. But he and RB Chris Brown, who didn't practice Monday due to his back injury, are not expected to play in the last preseason game Thursday against Tampa Bay.