Courting Chaos

As we've covered here in the past, the basic currency of basketball is the possession. Much like outs in baseball, teams have to use their possessions as efficiently as possible. On offense, this means taking good, high-value shots –at the rim and behind the arc¬– and getting to the free throw line. On defense it's about preventing these opportunities. Forcing bad shots and grabbing defensive rebounds is probably the most basic way to do this. The other way is to not let the ball get to the rim at all, causing a change of possession without the other team having a chance to score.

Changes of possession without a shot attempt come in two basic forms: live ball and dead ball. They're the results of blocks, steals, charges drawn, shot clock violations and random dribbles off of a foot. Live ball changes of possession are more valuable than dead ball changes of possession. The beauty of these plays is they not only end an opponent's possession, but they also allow a team to get out in transition against defenses that aren't set. The NBA's least efficient transition offense this season, 1.016 points per possession, is still more efficient than the top halfcourt offense, .982 points per possession.

This season, the Miami HEAT have the second most efficient transition offense in the NBA. Transition opportunities have accounted for 13.2 percent of HEAT possessions, good for 12th in the NBA, and a touch below last season's 14 percent figure. The open court is good to the HEAT, which isn't surprising.

The HEAT get in the open court by creating chaos, situations that Coach Erik Spoelstra likes to refer to as skirmishes. These skirmishes are live ball changes of possession that get opponents on their heels and cause all kinds of trouble.

Chaos Percentage

Blocked shots are generally good events for a defense. They prevent shots getting to the rim and possibly discourage opponents from taking the same shot again. However, blocks as logged in the box score are incomplete. Many blocks result in changes of possession, but it's probably not as many as we originally thought. On average, the defense gathers possession after a blocked shot 57-percent of the time. This distinction is important to note because it allows us to properly value blocked shots.

Steals result in a change of possession 100 percent of the time. They're extremely valuable. It stands to reason that a team that combines a high number of blocks and steals will have a good defense. To measure this, we're going to create something called "Chaos Percentage." To calculate it we're going to find just how often teams create live ball changes of possession, through either blocks with retained possession or steals.

The NBA data site nbawowy uses play-by-play data to determine how often a player's blocks are retained by his team. We took the next step combined the individual percentages to calculate team percentages. Using these numbers, we calculate live ball changes of possession:

Live Ball Changes of Possession = (Defensive Reb% After Blocks x Blocks) + Steals

Simple enough. Next, we have to calculate opponents' possessions. This is done using the same formula that uses:

Opponent Possessions = (.44*FTAs) + FGAs + TOs – ORebs

We use these two figures to find a team's Chaos Percentage:

Chaos Percentage = Live Ball Changes of Possession / Opponent Possessions

The higher the Chaos Percentage, the more often a team turns an opponent possession into it's own without the clock stopping. These are extremely valuable plays. They end possessions and often lead to easy baskets.

Below is a scatter plot of every team from 2005-2013's Chaos Factor plotted with their corresponding Defensive Efficiency (points given up per 100 possessions) Seasons prior to 2013 use the 57-percent estimation for possession after blocks. The 2013 season uses exact figures.

There's a very clear positive relationship. This means a higher Chaos Percentage usually results in a stingier defense. That's not always the case, but it's the general trend. Clearly, chaos matters.

Last season, the HEAT caused more chaos than all but two teams. The HEAT finished third in steals and tenth in blocked shots. This season, the HEAT have seen a slight dip in blocked shots, but are creating steals at about the same rate. This wasn't the case earlier in the season. The HEAT initially struggled to generate steals. In mid-January, the HEAT were 15th in the NBA in Chaos Percentage. Since then, they've ascended to 8th.

Since February 3rd, which was the start of the HEAT's 27-game winning streak, the HEAT have been particularly stingy on the defensive end, allowing just 99.2 points per 100 possessions, good for fourth in the league during that stretch. It shouldn't come as a surprise that the team's Chaos Percentage during that span has also been elite. Over the last 38 games, the HEAT have forced live ball changes of possession on 12.96 percent of opponent possessions, good for third in the NBA behind the Denver Nuggets and Oklahoma City Thunder.

Here's a graphic that charts the running Chaos Percentage and defensive efficiency for the HEAT. As you can see, as the Chaos percentage increases over the season, the defensive efficiency drops along with it:

Early in the season, the HEAT's Chaos Percentage dip from the previous season had affected both sides of the floor. Shot attempts that follow steals have the highest effective field goal percentage according to By creating chaos with higher frequency, the HEAT have enjoyed their best offensive stretch of the season, good enough to give them the top offensive efficiency in the NBA since February 3rd. Defensively, the difference is clear. Opponents are getting fewer shots to the rim, and as such are scoring less frequently. It's been a win-win turnaround for the HEAT.

The reasons for the rapid improvement are hard to pinpoint. The HEAT haven't changed their defensive principles, they're just executing at a higher level. The team's defensive energy has improved and the rotations that were a little loose in the opening months of the season have tightened significantly.

There's an advantage to creating your own chaos on the court. A team's offense and defense both perform better when live ball changes of possession are created. If the last 38 games are any indication, the HEAT, with a full complement of players, are back to causing as much chaos as any team in the league, which bodes well come playoff time.


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