Ryan Shazier of the Pittsburgh Steelers reacts as he is carted off the field after a injury against the Cincinnati Bengals during the first half at Paul Brown Stadium on Dec. 4, 2017 in Cincinnati, Ohio John Grieshop/GETTY

Pittsburgh Steelers linebacker Ryan Shazier remains hospitalized as his team takes on the New England Patriots Sunday. Shazier’s Dec. 4 injury in a game against the Cincinnati Bengals ended his season.

Shazier, 25, sustained a vicious back injury when he lowered his head to hit Bengals wide receiver Josh Malone. Shazier immediately clutched his back and was immobilized by medical staff before being carted off the field.

Cameras caught Shazier at Heinz Field from a suite and was greeted with a big reception from Steeler fans. CBS sideline reporter Tracy Wolfson said Shazier hasn't had interaction with the team before the game, implying that he wanted to surprise the team with his presence. Shazier was seen waving a yellow "terrible towel."

Shazier was at the University of Pittsburgh Medical Center. He received spinal stabilization surgery there earlier this month and Thursday the hospital said that he was officially beginning rehabilitation.

“He’s in great spirits and working hard,” said Steelers coach Mike Tomlin Wednesday.

The extent of the damage done and long-term neurological implications, if any, of Shazier’s injury have not been disclosed. Spinal cord injuries can lead to weakness or paralysis below the site of the injury, according to the Mayo Clinic.

Orthopedic surgeon and former head team physician for the Chargers David Chao wrote in a column that keeping Shazier in the hospital for rehab indicated the severity of his injury.

“Of course, his being in the hospital and needing to rehabilitate is worrisome, as it indicates we do not have the best-case scenario of full recovery. Any neurologic recovery that does not come quickly – in the first 24-48 hours – often takes months of hard work to improve,” wrote Chao in the San Diego Union-Tribune.

Chao, who is not involved in Shazier's care, said that the evidence so far indicates that Shazier currently may not have the full use of his legs.

Shazier was placed on injured reserve Dec. 12, ending his season.

“Unfortunately Ryan will not be able to contribute on the field during the remainder of this season,” said Steelers President Art Rooney II in a team statement. “However, even off the field Ryan will continue to be one of our team leaders. We know his spirit and positive outlook will help him to continue in his recovery, as well as serve as an inspiration to our team.”

Some of Shazier’s teammates wore special cleats to honor him last week.

“Emotionally we understand one of our brothers is down,” defensive end Cameron Heyward told the Worcester Telegram and Gazette. “We’re just going to pray for him and play for him as well. You want to keep getting wins for him and keep making him proud.”

The Steelers take on the Patriots Sunday afternoon in Pittsburgh. The Steelers lead the AFC and the Patriots are seeded second, both teams are in position for first-round byes in the playoffs.

Patriots special teams captain Matthew Slater told the Worcester Telegram and Gazette that their team was pulling for Shazier.

“I’d like to say we’re all praying for Ryan. Nobody likes to see that. As competitors and as competitive as we are, we don’t want to see anyone get hurt on the football field, especially an injury like that. So we’re definitely praying for him,” said Slater. “But it is a reminder of the violent nature of the game that we play, and some of the things that can happen out there on the football field, and you can only pray that every time you take that field, that you’re able to walk off of it.”