The good news is the Chiefs quarterback was doing better less than hour after the game. The bad news for Kansas City is that Green might be knocked out for at least a week with a key division game ahead next Sunday against the Broncos.
"Obviously, it was a pretty severe head trauma, but he had all of his senses and feeling in his arms and legs," Chiefs president Carl Peterson said. "Actually, when he did wake up, he remembered every play except the one that knocked him out. He's in the hospital right now, but the preliminary X-rays -- and they did them of the neck and head -- are negative. So we're being optimistic and hopeful."
On second-and-2 with 4:52 remaining in the third quarter, Green scrambled to his right and started to hook slide. As he did this, Geathers, possibly assisted by a push from behind from Chiefs receiver Eddie Kennison, delivered a hit on Green. What was worse than the hit was the impact of Green's head snapping back on the Arrowhead Stadium grass.
"He's a leader of this team and to lose a guy like him, that's big. That's reality, but at the same time, we've got to go to work. We've got 15 games left. It's a long ride."
Derrick Johnson, Chiefs LB
The double impact knocked Green out cold. Within seconds, trainers brought out a backboard, but it took another 11 minutes to get Green off the field, leaving a sick feeling in the hearts of his Chief teammates.
"I don't like to look at stuff like that," tight end Tony Gonzalez said. "That's not my thing. I get to feeling pretty weird when I go to the hospital for my [charitable] foundation. This was just like that. It was obviously not as tragic as something at Mercy Hospital, but it was the same type of thing because you didn't know what was going on."
Damon Huard finished the game and might have to be next week's starter against Denver. Though he's 5-1 as a starter, it's hard to imagine Huard running the offense as smoothly as Green, a master of throwing accurate timing routes.
Head injuries are a big concern leaguewide, which is one of the reasons why it might be tough for Green to play next week. With a bye week scheduled after the Denver game, there is a good chance the Chiefs will let Green sit, but that won't be decided for a couple of days.
"The good thing is nothing's broke," Chiefs coach Herm Edwards said. "He'll survive because he's a tough guy. I thought Damon came in and did a pretty good job once he got going. It was helmet to helmet and that's always tough. Officials will have to look at it on tape and we've been advised not to comment on officials' calls. I'm not going to 'He said' or what they should have done."
Geathers said the hit was unintentional. Though Geathers' hit could be subject to review, the Bengals are going to argue that Geathers couldn't stop because Kennison pushed him.
"It's an unfortunate situation and my prayers go out to his family and him and I hope he recovers," Geathers said. "We're just playing ball, flying around, and I know he understands that. He's played a long time. My best goes to his family."
Bengals quarterback Carson Palmer was troubled by the injury because Green had been helpful to him, talking him through his recovery from reconstructive knee surgery. Green had a similar comeback earlier in his career.
"It's tough in this kind of small fraternity of quarterbacks in this league when you see a quarterback go down like that," Palmer said. "You start praying for him and that's all you can do and hope for the best."
Long term, Green appears to be fine. The question is going to be how long he will be out.
"He's a leader of this team and to lose a guy like him, that's big," Chiefs linebacker Derrick Johnson said. "That's reality, but at the same time, we've got to go to work. We've got 15 games left. It's a long ride."
John Clayton is a senior writer for ESPN.com.