Pressure/Delay

immediate chase and pressure on the ball to slow down the attack until defense is regrouped and can win the ball back (pressure may be to drop off and stay deep)
deny and delay forward progress by closing gaps for passing and scoring chances – keep play in front

Cover/Support/Depth

defend vital spaces by tracking dangerous runs and cutting off passing lanes
provide cover/support to pressuring defender in case he is beaten
provide communication to pressuring defender
get numbers behind the ball

Balance

maintain defensive balance or shape by providing equal or greater number of defenders behind the ball while also positioning away from the ball to cover danger areas near the goal (cut off passing lanes and observe other attackers on the weak side; squeeze towards the ball from the sides)

Concentration/Compactness

squeeze the attack from back and front into a restricted area to make it easier to defend and regain possession of the ball (stay compact and keep spaces between defenders as small as possible)
concentrate on danger areas between the ball and the goal to close off gaps (avoid being stretched wide – defenders must not to follow players to the outside until ball is moved into that area

Composure/Control/Restraint

show patience and discipline in defending soccer on and off the ball by maintaining proper defensive techniques and positioning
wait for the attacker to make a mistake to be sure to win the ball