Buffalo Bills safety Damar Hamlin might have been a fraction of a second away from moving on to the next play.

Hamlin suffered a cardiac arrest Monday night when he collapsed on the field in Cincinnati, was administered CPR under life-or-death circumstances and hospitalized in critical condition after what one independent board-certified cardiologist saw as a collision at the time in the cardiac cycle when the heart is most vulnerable.

“That hit had to occur at a certain point in time that was only five milliseconds long,” said Dr. Marc Cohen, Chairman of the Department of Medicine at Newark-Beth Israel Medical Center. “If that hit occurred one millisecond after or before, this may not have happened.”

What looked like a routine (by NFL standards) tackle by Hamlin on Bengals receiver Tee Higgins resulted in Hamlin getting to his feet, adjusting his facemask and immediately falling onto his back as horrified players from both sides watched trainers, paramedics and doctors assist with his breathing and restore his heartbeat.

Bills safety Damar Hamlin went into cardiac arrest during “Monday Night Football” against the Bengals. Follow the New York Post’s live coverage for the latest news and updates on his condition.

Bills safety Damar Hamlin (3) suffered cardiac arrest after tackling Bengals receiver Tee Higgins (85) on Jan. 2, 2023.

One common medical explanation is commotio cordis, though that is considered more an instantaneous reaction that would be a challenge to explain how Hamlin rose to his feet.

Cohen’s expertise suggested several issues at play.

“There is a time in the cycle of the heart where we are at risk. If we were to tap the heart, we can cause the heart to go into ventricular fibrillation,” Cohen told The Post. “More likely than not, what happened is he got up and his rhythm became chaotic. That may have taken a few seconds to occur.”

Cohen also noticed on replay that Higgins stopped Hamlin’s chest when they collided, but Hamlin’s head snapped back and forth.

Josh Allen (17) and other Bills players react after Damar Hamlin’s collapse on Jan. 2, 2023.

“When your head goes ping-ponging, it’s very possible that a tremendous amount of adrenaline may be released,” Cohen said, “and that adrenaline triggers the heart to go into a chaotic rhythm, which we call ventricular fibrillation.”

The third possibility that occurred to Cohen from afar is similar to what was commonly seen in car-crash victims who slammed into the steering wheel before the popularization of the seat belt and airbag.

“You would tear your aorta at a certain point in your chest, where the rest of you is going forward, but your aorta is pinned down by some ligaments,” Cohen said. “That would cause a catastrophic tear.”

Bills safety Damar Hamlin after a game against the Titans on Sept. 19, 2022.

In all three possibilities, on-field defibrillation could have revived Hamlin’s heartbeat, but the unknown is whether the heart is pumping enough blood to the rest of the body, including the breathing center in the brain.

The vulnerable period within each cardiac cycle is only a few milliseconds long, when the heart is most susceptible to degeneration from a sudden physical impact.

The Bills released a statement on Tuesday afternoon that Hamlin spent the night at the intensive care unit at the University of Cincinnati Medical Center and remained in critical condition. The Bills-Bengals game was suspended and will not be resumed this week.

Cohen credited the first-responders for quick action on the field and said this should be a “wake-up call” to make sure safety equipment is readily available throughout cities to encourage bystander CPR.