Houston Texans coach Gary Kubiak, 52, collapsed as he was walking off the field at halftime of the team's game with the Indianapolis Colts.
Kubiak was put on a backboard and stretcher and sent to a hospital, though the team would not identify which one to NBC.
Texans assistant coaches were told that taking Kubiak to a hospital was a precautionary measure and that he did not have a heart attack, NBC reported. He did not lose consciousness and his family was with him at the hospital.
"He had an episode; he was light-headed and dizzy," Houston general manager Rick Smith said in an interview on NBC. "He was evaluated by a number of specialists ... he is awake and coherent.
"We have to assess ... obviously, there's a lot of info," Smith said. "Hopefully, Gary will be back with us tomorrow."
Colts owner Jim Irsay tweeted: "Big time prayers for Coach Kubiak...God bless his healthy return and ease his family's worry and concern."
Wade Phillips took over as head coach. The Texans led 21-3 at halftime but lost 27-24.
"There was a lot of unknown," Phillips said. "Everything was unknown as to what was going on and what happened to Kub. (Offensive coordinator) Rick Dennison obviously called the plays from the press box. We had to adjust as far as the head coach not being there. But it was a shock to everybody."
Texans quarterback Case Keenum said players were concerned for their coach's health.
"We were all very worried," quarterback Case Keenum said, according to The Associated Press. "When we went back out they told us he was ... stable. We were all upset about that but trying to stay focused at the same time."
Earlier this weekend, Denver Broncos coach John Fox was taken to a hospital in the Charlotte area after feeling light-headed while playing golf. He will have surgery on an aortic heart valve replacement next week, which will keep him away from the team for "at least the next several weeks," the team announced late Saturday night. Colts head coach Chuck Pagano missed much of last season after being diagnosed with acute promyelocytic leukemia.
Kubiak has long been known as a top offensive coach, mentoring quarterbacks in Denver under Mike Shanahan and now Matt Schaub - and Case Keenum - in Houston. Kubiak has had no known public health problems.
Kubiak was hired in 2006, along with general manager Rick Smith, after the Texans finished a franchise-worst 2-14. Smith spent 10 years with Kubiak while the coach was offensive coordinator of the Broncos. Smith was Denver's defensive assistant for four seasons before moving into the front office for his last six years with the Broncos.