The scariest possible sports moment

I have been gripped by something that has nothing to do with the NCAAs at all. It does have with a tournament, the FA Cup in England. Bolton Wanderers midfielder Fabrice Muamba collapsed in the 41st minute, needing to be resuscitated as he was stretchered off the field.  Muamba is thought to have suffered a massive heart attack, and he is "critically ill" and at a place called the London Chest Hospital.
This isn't the first time that there has been a cardiac incident on the pitch in a European soccer match. The history with such incidents isn't very good either. It's a terrifying incident that nobody ever wants to experience, and we can only hope Fabrice can recover, so he can raise his young son, soccer be damned.