Thank you for responding so quickly to a weekend question.... after further investigation, we have learned more details concerning the poor sportsmanship/pushing issue. I didn't witness the event, but my daughter did, and she confirmed my son's story. The girl in question intentionally threw a ball and hit our son, after the game was over. His response to this was the push (still completely unacceptable!). His consequence is the same ("lockdown"). Sports season is over. What's an appropriate length of time for his lockdown?
On the bright side, because of this issue, we've had numerous important conversations with our daughter - never okay for a boy to be physically aggressive, never okay for a child to instigate trouble from another child, etc. Thanks again - and I will not beat this dead horse any longer!