I completely agree with Jubee; your concern at this point is premature. Wait and see how practice and games go. Give the coach a chance to do his job. It's entirely possible this kid could excel at soccer, it is a very physical and aggressive sport.
If you do see things that trouble you and it doesn't appear the coach is handling them then talk to the coach about it.
ETA - I would be careful about talking to the mom about behavior on the soccer field. Take it to the coach and let them handle it. DH coaches my daughter's 2 soccer teams, and my son is on a select team and a rec team. It is my job as a parent to be supportive of my kids, supportive of the team, and supportive of the coaching staff - it is not my job to address the playing style or behavior of another child on the team.