They may still be required to run with opponents who make forward runs toward their goal, but generally they attempt to defend in the left, center, and right midfield areas of the field.
Alternatively, a central midfield unit may be organized to defend on a zonal basis. This means that, largely, players in this unit defend against opponents that come into their personal zones in the midfield areas of the field and pass on opponents who move their position across the field of play to the next midfield player in the zone. They may still be required to run with opponents who make forward runs toward their goal, but generally they attempt to defend in the left, center, and right midfield areas of the field.