Bill Kollar, Houston Texans assistant head coach/defensive line, left Soldier Field prior to the Texans 13-6 win over the Chicago Bears because of a shortness of breath and was taken by ambulance to a local hospital.
Initial tests found that Kollar had a blood clot.
Head Coach Gary Kubiak said Kollar will spend at least one more night in the hospital in Chicago for further tests.
"He's doing fine," Kubiak said. "He had some shortness of breath before the game, wasn't feeling well and we took him to the hospital for some tests.
"He's still going through some more tests. I want everybody to know he's doing well, but he will spend a day or two here and then be back. I know Bill is very proud of our defense and how we played and we really missed him. We got a (game) ball waiting for him.
"So we battled for him. I want you to know that, but he's doing just fine."
Kollar was definitely on the minds of his players during the game with the Bears.
"I became honorary coach/player," said defensive end Antonio Smith. "It felt good to be calling the calls out there.
"I might of messed up. Bill is going to get on me when he comes back to work. None of us really knew what had happened untill after the game. After Kub (Kubiak) told us everything is going to be all right, we know he is going to be all right. He's going to be there next week on us like he is always on us."
Defensive end J.J. Watt said it was not easy for the team to get that kind of news about one of their coaches.
"It's a tough thing to hear right before you go play a football game," Watt said. "We're glad he is going to be okay.
"It was weird not having him out there. Didn't think I would miss him, but I actually missed him out there on the sidelines. He's a great football coach and a great guy. We're happy to get this win for him. I know he was in that hospital bed kicking and screaming at the TV the whole game.
"I'm really happy to get the W for him."