What is a sweeper and what do they do on a soccer team?
A sweeper is usually the last defensive person back besides the goalie. If the ball gets by everyone else it is up to him/her to get the ball away from the goal. Also the sweeper needs to be fast in case he/she gets caught up to far on the field and needs to get back really quick. The sweeper is also the person responsible for keeping the fullbacks at the right spot so you can catch the forwards offside.
The sweeper is a player, usually a defender, designated by the team's captain to advance along the side of the field behind the offensive player who has the ball.