MARK LEATHER
Former Premier League physio
It's unlikely that being hit by the ball could have killed Van Persie. But being struck that hard from such a short distance could have knocked him out. I’ve seen players knocked out by free-kicks struck from 10 yards away.
If you are unconscious, there is then a risk of trauma to the brain. A blow that fierce is like being hit in boxing - the damage is unpredictable. It can lead to internal bleeding and permanent damage, or there can be just an aching head.