A Kansas City Chiefs player suffered a medical emergency on Thursday morning ... and now, the team's revealed it's canceled its planned practice in wake of the scare.
The player has not yet been identified publicly by the organization -- nor has KC given an update on his status. But, according to NFL Network's Tom Pelissero, it was "a backup defensive lineman" who suffered a seizure in a special teams meeting.
Pelissero reported the athlete went into cardiac arrest ... but, thankfully, trainers raced to his aid, got him in an ambulance, and he's now currently in stable condition.