Here is a drill that works on ball defense that I stole from Kevin Eastman (assistant coach, Los Angeles Clippers).
SET UP: To set the drill up, divide the court into 4 different segments. For my team, I split each half court in half, as well as use the middle of the court sideline to sideline. Have the player partner up.
STEP 1: One partner is on offense for one minute, the other partner is on defense for one minute. The defender has to stay one arm length away from the offensive player at all times. The offensive player will attack the defensive player while the defender must either step-slide their feet or use a turn and run step to stay chest to chest.
Step 2: At the end of one minute, switch partners so that the dribbler is now on defense and the defense is now on offense.
Step3: Repeat as many times as needed. This drill will show you who wants to compete and guard, and who wants to slack and lag.ere is video of my team using this drill to start practice:
Here is video of my team using this drill to start practice: