The Denver Broncos’ miraculous near-comeback was cut short on Sunday when Russell Wilson suffered a ghastly head injury that forced him to exit the game, and enter the NFL’s concussion protocol.

According to head coach Nathaniel Hackett, Russell Wilson even appeared to be unconscious for a moment following the hit.

“I believe [he was unconscious]—it looked like it on the film,” Hackett said. “I haven’t gone in and talked with the medical doctors entirely. We will get all those medical reports as we move forward. For us, his safety is the No. 1, biggest priority for us. We want to be sure we do what’s right for him.”

Now, his status for the Denver Broncos’ Week 15 matchup with the Arizona Cardinals is in doubt.

Coach Hackett said the Broncos are going to do everything by the book, and listen to the doctors when it comes to deciding Wilson’s status for Sunday.

Russell [Wilson] is in a concussion protocol,” Hackett told the media on Monday. “We’re going to do everything the way that the medical doctors say—the independent doctors. We’re going to do every single thing. His safety is by far the No. 1 most important thing. We’ll continually talk to him—and to everybody else—about that and make sure we do the right thing.”

There is some optimism that he could play on Sunday though, and Wilson is already working with independent NFL doctors to get that sorted.

“He’s going through the concussion protocol that we have in place, that the NFL has in place, that we all have in place to make sure that he’s healthy and he’s good,” Hackett shared. “He felt great today. When we saw him, he looked great, but we want to be sure that we do everything the right way.”

No matter who starts under center for the Denver Broncos on Sunday, they’ll likely be squaring off against Colt McCoy, after Kyler Murray suffered his own tragic injury on Monday night.