In addition to getting their first game action against NBA-level talent, Summer League is an opportunity for players to get use to some of the rules that differ in the NBA as opposed to college basketball.  For big men, the toughest rule change they are going to have to deal with is the defensive three second rule.  This rule is exclusive to the NBA and it is defined as follows:

a. The count starts when the offensive team is in control of the ball in the frontcourt.

b. Any defensive player, who is positioned in the 16-foot lane or the area extending 4 feet past the lane endline, must be actively guarding an opponent within three seconds. Actively guarding means being within arm’s length of an offensive player and in a guarding position.

c. Any defensive player may play any offensive player. The defenders may double-team any player.
d. The defensive three-second count is suspended when: (1) a player is in the act of shooting, (2) there is a loss of team control, (3) the defender is actively guarding an opponent, (4) the defender completely clears the 16-foot lane or (5) it is imminent the defender will become legal.

e. If the defender is guarding the player with the ball, he may be located in the 16-foot lane. This defender is not required to be in an actively guarding/arm’s distance position. If another defender actively guards the player with the ball, the original defender must actively guard an opponent or exit the 16-foot lane. Once the offensive player passes the ball, the defender must actively guard an opponent or exit the 16-foot lane.

It is something that Derrick Favors struggled with in his first game as a pro:

Here, Favors meets his man, Cedric Simmons at the top of the key.  Simmons is cutting through the paint, and Favors gives him a bump for his troubles.

Simmons gets to his spot on the court, and Favors is in help position.  This is a perfect example of a defender actively guarding a man.  As long as Favors stays here within arms-length of Simmons, he can stand in the middle of the lane as long as he wants to.

However, as the ball goes to the opposite corner, Favors needs to head more towards the middle of the paint to be in proper help position.  He gets to the middle of the court, but he also seems to be aware of the defensive three second rule.  He tries to get within arms-length of Simmons.  However, Simmons is a guy who has NBA experience and knows the rules.  He smartly takes another step back.  The purpose of this is to either force Favors out of the lane or draw a three second call.

Here, Favors is two to three arms length away from his man Cedric Simmons.  The ref is being blocked by the scoring graphic, but he is staring right at Favors.  What Favors needs to do here is what most big men in the NBA do.  He needs to take a quick step out of the paint and get close to his man, and then quickly return to the paint.  That qualifies him as actively defending someone, and then the defensive three second clock restarts.

However Favors doesn’t leave the lane and he is whistled for the defensive three second violation.  This is a terrific learning experience for the young 18 year old.  He seemed aware of the rule, but he was unable to properly execute his defense to avoid the call.  What the Nets’ coaching staff is hoping to do is look over the game tape with him, teach him the proper techniques, and hope that he files this away in the back of his mind for when he is in this situation once again.  Here is the play in real time: