I feel that concussions can be “prevented” in practice with contact limits and proper technique during drills.  The other two incidents, thus far, I deemed preventable occurred in practices and were concussions.  One player was hit by a teammate during a non-contact soccer drill as a “joke” and the other did not use good judgement and ran into a pile and was rocked.

via Constantly Learning and Watching: There Is a Time to Act – The Concussion Blog