Rotating

The offense works to create an advantage, and then aims to capitalize on that advantage. That means the defense does the opposite: they work to not even allow an advantage in the first place, and then if they fail at that, they work to neutralize any advantage that was gained.

Think about a ball handler going against a defender. The first goal of the offensive player is to gain an advantage: to try to create an opening to take a shot, or get a step past the defender on a drive. The defender’s goal is to not allow any advantage. When people talk about defense in basketball, this is what they typically think of: guarding the ball and stopping any advantage from being created in the first place.

But let’s say the offensive player manages to get past their defender. In that case, the defense has to react to that advantage and try to neutralize it. That’s where help comes in. The defender’s teammates need to move to try to stop the advantage; otherwise they will allow a layup. So a teammate will slide over to get in front of the driver, providing help.

When that happens, the offensive player might force up a shot, or try to drive through both players, but their odds of success are much lower than before the help arrived. The defense, by helping, has mostly neutralized the advantage. But not completely, because that help has opened up a teammate. So if the offensive player passes to their now open teammate, then the advantage is maintained. The defense has to rotate again in help or the offense will get an open shot. They have to help the helper.

At the lowest levels of basketball, that first line of help might be enough to neutralize the advantage. But at the NBA level, offensive players are so good that they anticipate the help and will make the right pass when that help opens up a teammate. So the better the offense, the more defenses have to focus not just on the initial help, but on how to cover for their helping teammates, to help the helper. This second line of defense is not just about the help, but about the rotations in behind the help.

Perimeter Rotations

The most straightforward kind of rotation on the perimeter is a full rotation. A full rotation is a chain reaction: if an offensive player on the perimeter catches a pass, the player nearest to them will rotate over and help. The player who is now open will be taken by the next closest player.

In this case the player who initially helped does not aim to recover to their initial matchup. Instead they recover to the end of the rotation chain, and the matchups are now switched.

A full rotation involves a lot of movement and scrambling, and therefore good offenses can find open shooters with good ball movement. That’s why the use of full rotations has declined a lot in the NBA. But when executed with the proper effort and precision it can make it very hard for offenses to get open looks.

Instead, the NBA started trending toward a help and recover model. In this method of help, the player who helps is responsible to recover to their matchup and contest the shot as best they can.

They get support from the next player in the help chain not with a rotation but with a stunt. That player fakes as if they’re going to help, trying to freeze the pass receiver and buy time for the receiver’s defender to recover to them. After the stunt, they recover to their own matchup. You’ll often see this as a stunt into the passing lane to make the quick pass even more difficult.

When executed properly, then, the stunt and recover doesn’t fully open up any shooters, particularly if the offense doesn’t have good spacing. NBA teams, though, have figured out how to design sets that position their players such that the distance it requires to stunt means that defenders can’t stunt effectively without leaving their matchup open. With so much shooting and spacing on the court, stunts in rotation are not as common. Teams instead will either rotate more aggressively, or not rotate at all, based on the matchup.

In the case of no rotation, the defense is just willing to leave that player open on the perimeter.

Rotations are reflexive and happen very quickly, so players need to be acting off of instinct as much as anything. But coaches will still try to choose their style of rotation based on who catches the ball on the perimeter.

“KYP”, – a coach will say. “Know your personnel”. Great defenses don’t just blindly follow rules, but tweak their rules depending on who has the ball. Coaches may highlight a few major threats that they want to fully rotate to, and a few non-threats they want to avoid rotating to, and trust their players can follow the scouting report in the heat of the moment.

Interior Rotations

The most important situation for the defense to help the helper happens when help comes from a defender near the rim. In that case, the offensive player they’re guarding is perfectly positioned for a layup, dunk, or offensive rebound. That means if the defense doesn’t help the helper and rotate to defend the newly open player, the offense is likely to get a very high percentage shot.

This kind of helping the helper is called a sink, where a perimeter player sinks down to take away the interior pass.

The nearest other helper then has to cover for the player executing the sink by filling, aiming to position themselves so that they can rotate to whoever gets the ball.

After executing this sink and fill, there are two main ways for the defense to recover on a pass out. They can simply recover back to their original matchups. Or they can x-out, where they exchange matchups, recovering in an “X” shaped pattern.

An x-out is a method that allows the defense to recover based on who is closest to the player receiving the kickout pass. If the fill player is closer to the receiver, they will rotate and trust their teammate to take their original matchup. In that way it’s somewhat like a full rotation: it scrambles the matchups, but is more likely to cover open players.