Effective Field Goal Percentage Breakdown

Along the same lines as my last post I decided to breakdown each teams effective field goal percentage to determine what impact shot selection and shot making abilities have on their eFG%.  To do this I determined what each teams eFG% would be if they shot at the league average in each of the 6 shooting zones from my previous post(at the rim, short range, mid range, long 2s, corner 3s and non corner 3s). I call this the average shooting eFG%.  Subtracting this number from the team's actual eFG% gives what I call the shooting factor - how much better (or worse) would their eFG% be if they were an average shooting team.  The bigger the number the better shooting team they are.  To get the shot location factor just subtract the league eFG% from the team's average shooting eFG%.  This represents how much better (or worse) than average the team is due to their shot selection.  The bigger the number the better their shot selection.  The results are below:

 

My last post showed that Houston and Denver were the 2 best teams at getting efficient shots.  This table shows that as well.  Both teams are in the top 7 in eFG% despite being average/below average teams at making shots.  I also talked about how OKC, Golden State and Dallas all have a good/very good eFG% despite average/poor shot selection and a possible reason why.  This table confirms that possible reason as those 3 teams have the 2nd, 6th and 5th best shot factors respectively.  Detroit is an interesting team as they have the 4th best shot selection factor but the 4th worst shooting factor.  Not surprisingly my Toronto Raptors have the 4th worst shot selection factor and a slightly above average shooting factor.

Team shot locations and offensive efficiency

The most efficient shots in basketball come from very close to the basket and from behind the 3 point line.  The least efficient shot in basketball is the long 2.  Knowing this, it should be the case that teams that attempt a lot of long 2s should be among the least efficient offenses in the league while teams that get a lot of field goal attempts near the rim and from beyond the arc should be the most efficient.  I decided to look at these relationships in more detail using data from the 2012-13 NBA regular season.  To do this I broke down team shooting locations into different shooting zones: within 3 feet of the basket, 3-9 feet from the basket (short range), 9-15 feet from the basket (mid range), 2 point shots from 15+ feet from the basket (long 2s), corner 3s and non corner 3s.  For each team I looked at the percentage of their field goal attempts in each shooting zone.  For this study I only cared about long 2 point attempts (inefficient shots) and the combined total of 3 point attempts and attempts within 3 feet of the basket (efficient shots).

First lets look at the efficient shots.  Here are top 5 teams in terms of percentage of their shot attempts that are efficient (within 3 feet of the basket or 3 point shots):
Houston: 71.6%
Denver: 65.6%
New York: 64.9%
LA Lakers: 61.0%
Detroit: 60.2%

In terms of offensive efficiency these 5 teams rank 6th, 5th, 3rd, 8th and 21st respectively.  It is also worth noting that the most efficient offense, Miami, is 6th best at getting efficient shots.  So 5 of the top 6 teams at attempting efficient shots are in the top 8 efficient offenses in the league.  Detroit seems to be an interesting case of a team attempting a lot of efficient shots but not having an efficient offense.  A quick look at their effective field goal percentage suggests a probable reason for that.  Their effective FG percentage is 48.7% which is 19th best in the league.  This suggests that even though they are taking a lot of efficient shots they don't appear to be making many of them and as a result their offense struggles.  Another interesting team to look at is the Oklahoma City Thunder.  They have the 2nd most efficient offense, the 3rd best effective FG% but are in the middle of the pack in efficient shot attempts at 15th.  Looking at shooting percentages by shooting zone the Thunder are very good at mid range shots and long 2s so their ability to make inefficient shots appears to make up for the fact that they are just an average team at attempting efficient shots.

Now lets look at the bottom 5 teams at attempting efficient shots:
Washington: 47.9%
Memphis: 48.8%
Philadelphia: 49.2%
Dallas: 49.3%
Golden State: 50.1%

These teams rank 30th, 19th, 26th, 12th and 10th in offensive efficiency.  There doesn't appear to be as strong a connection here as there was with the teams that take a lot of efficient shots.  Despite being among the worst 5 teams at getting efficient shot attempts both Dallas and Golden State have above average offenses.  Golden State leads the league in 3 point field goal percentage are also the 5th best shooting team in the league at long 2s.  Similarly, Dallas is 6th at 3 point field goal percentage and 3rd at long 2 shooting percentage.  So both these teams make up for not taking a lot of efficient shots by being very good jump shooting teams.

Here is a plot of the percentage of efficient shots vs offensive efficiency:

Now let's look at the teams that shoot the most and least long 2s and see how efficient or inefficient these teams are on offense.

The 5 teams with the highest percentage of long 2s taken are:
Boston: 25.7%
Phoenix: 25.2%
Philadelphia:  25.1%
Chicago: 24.8%
Golden State: 24.3%

These teams rank 20th, 28th, 26th, 24th and 10th in offensive efficiency respectively.  Other than Golden State, who was already talked about above, these teams would all be classified as poor offensive teams.  Thanks in large part to Kevin Garnett, Boston is the 2nd best team at making long 2s.  The fact that the team that shoots the most long 2s shoots them at a very high percentage but can still only manage to be the 20th best offense would seem to suggest that the long 2 is not a shot teams should be looking to take.

The 5 teams with the lowest percentage of long 2 attempts are:
Houston: 11.1%
Denver: 12.6%
LA Lakers: 16.8%
Brooklyn: 16.8%
San Antonio: 17.5%

These teams are 6th, 5th, 8th, 9th and 7th respectively in offensive efficiency.  Not surprisingly the teams that shoot the lowest percentage of long 2s are all teams with a high offensive efficiency.  The 2 most efficient offenses are Miami and Oklahoma City.  Both of them are in the middle of the pack at attempting long 2s but they make up for that by being 1st and 7th at making long 2s. 

Here is a plot of the percentage of long 2s attempted vs offensive efficiency:

All of this shows that if a team wants to improve offensively they should design their offense around getting as many shots close to the basket and from behind the 3 point line as they can while limiting their long 2 point attempts.  None of this should come as a surprise but it's still good to see the actual numbers and visual representation of the relationship between where teams take their shots and their offensive efficiency.  It is interesting to see the Houston Rockets, a team known for really embracing advanced analytics, attempt the fewest percentage of long 2s and also take by far the highest percentage of the most efficient shots.  I only have shot location data from this season but it would be interesting to look at these numbers over multiple seasons.

Amir Johnson: Quietly going about his business as the Raptors most important player

As the Raptors finish up their 5th straight season without making the playoffs, much of the talk is about next year.  Will Dwayne Casey and Bryan Colangelo be back as coach and GM?  Can DeMar DeRozan and Rudy Gay play together?  How much will Jonas Valanciuanas and Terrence Ross improve over the summer?  Of all the players being talked about there is one name that never seems to come up - Amir Johnson.  For all the talk about Rudy Gay and DeMar DeRozan, Amir Johnson is by far the biggest difference maker for the Toronto Raptors.  Take a look at the team efficiency and four factors stats for both offense and defense when Johnson is on and off the floor.

Offensive Efficiency and Four Factors

Defensive Efficiency and Four Factors

As you can see from the numbers above the Raptors improve significantly on both offense and defense when Amir Johnson is on the floor.  What these numbers show is that when Amir Johnson is on the floor the Raptors have a good offense and a good defense and when he is off the floor they have a mediocre offense and a mediocre defense.  Kyle Lowry is the only other Raptor that improves the team both offensively and defensively but those improvements are nowhere close to the difference Amir Johnson makes.  You won't see the high flying dunks or game winning shots that you get from DeMar DeRozan and Rudy Gay.  You also will never see Amir Johnson sulk and complain to the refs when a call doesn't go his way like you see from Rudy Gay.  All you will see from Amir Johnson is production.