Indicators of NBA

Playoffs Success

The NBA finals are one of the most watched sporting events in the world, with viewership peaking at 16.9 million during the 2022 NBA finals. As an NBA fan and casual sports bettor, I was interested in seeing the biggest indicators of success in the NBA playoffs and whether or not I could use those indicators to narrow down the list of potential NBA champions for the 2022-2023 season. I collected the advanced statistics for each NBA season from the 2011-2012 season to the 2021-2022 season from Basketball Reference and analyzed the data to hopefully gain some insight into what makes an NBA champion.

As a starting point, I was interested in seeing the offensive and defensive ratings of previous championship winners, and whether or not there have been any trends that can be observed over the past 11 seasons. Offensive rating is an estimate of the number of points a team scores per 100 possessions, while defensive rating is an estimate of how many points a team allows per 100 possessions. To investigate this, I created a line plot that visualizes the offensive and defensive ratings of NBA champions, and as shown in the plot, the offensive rating of NBA champions has been on an upward trend while the defensive rating of NBA champions has been on a downward trend. This is something that we would expect to see, as teams have become more offensive minded over the last few seasons. Keeping the information shown in the plot in mind, we can expect this year's NBA champion to have a defensive rating lower than 112 (lower is better) and an offensive rating that is greater than 112.

To get a better idea of what championship teams look like, I decided to do PCA on the data. I then got the weights of the original variables to determine which statistics are the strongest indicators of whether or not a team wins a championship. The original variables with the largest weights are margin of victory, simple rating system, and net rating. I then found the correlation coefficients for each variable with whether or not a team won the championship to further determine the most important statistics in predicting success in the playoffs. The variable with the highest correlation with NBA championship victory was margin of victory, which was closely followed by net rating, simple rating system, and effective field goal percentage. Margin of victory, net rating, and simple rating system are very similar in terms of what they are measuring, so they are strongly linearly correlated. Because of this, I decided to look only at margin of victory and effective field goal percentage instead of all four variables.

As shown in the scatter plots for the 2012 season through the 2022 season, all NBA champions had high average margins of victory and high effective field goal percentages relative to their competition. Using this information, we can determine which teams in the 2023 NBA playoffs fit this criteria of an NBA champion. Out of the teams still left in the playoffs as of early May 2023, it seems as though four out of the eight teams have average margins of victory and effective field goal percentages that are high enough for them to have a considerable chance of winning the NBA finals. These teams are the Boston Celtics, the Denver Nuggets, the Golden State Warriors, and the Philadelphia 76ers.

After determining the four teams who met the criteria of NBA champions in terms of margin of victory and effective field goal percentage, I decided to plot those teams’ offensive and defensive ratings. As explained earlier, offensive rating is a measure of how many points a team scores while defensive rating is a measure of how many points a team gives up. A larger difference between offensive and defensive ratings should correlate with being a better team, and therefore also correlate with having a better chance of winning an NBA championship. As shown in the plot, the Warriors have a low offensive rating and a high defensive rating, suggesting that they have a lower chance of winning this year than the other three teams. The Celtics, Nuggets, and 76ers all have very similar offensive ratings, but the Celtics are considerably better on defense than the other two.

After considering all of the factors discussed earlier, the Celtics are the team that best fits the criteria of a traditional NBA champion. They have both a top three offensive and a top three defensive rating, and they have the largest difference between offensive and defensive rating in the NBA this season. On top of that, they have a top-five effective field goal percentage. As the runner-up last year, I believe the Celtics will put it together these playoffs and emerge as NBA champions.