Predicting the 2018 NBA playoffs is a mess. The list of problems starts with these issues:
- Elite players like Steph Curry and Joel Embiid will start the playoffs injured.
- Golden State has not performed up to expectation this season, as their defensive efficiency dropped from 2nd to 11th from 2017 to 2018.
- Kyrie Irving is out for the entire playoffs.
Usually, I take my team rankings that include data from all regular season games and calculate championship probabilities. However, that will not work this season.
Here’s how I approached predicting the 2018 NBA playoffs.
First, I took the game results from the season and kept only games in which teams had all their key players. For example, Golden State had 29 games in which Steph Curry, Klay Thompson, Kevin Durant and Draymond Green all played.
This reduces the set of games, but it gives a better picture of how a team might perform with its top players. These numbers assume Golden State and Philadelphia will have Curry and Embiid respectively. With this reduced set of games, I take margin of victory and adjust for schedule with my ranking algorithm.
Second, I take the closing point spreads in the markets since January 1st and perform the same filtering process with top players. I generate market rankings by adjusting these spreads for schedule.
I decided to focus on the last part of the season to get a more recent picture of team performance. The markets still believe in Golden State, but not as much as in earlier in the season.
Then I blended these two rankings to give the following rankings of playoff teams. The rating gives an expected margin of victory against an average NBA team on a neutral court.
1. Houston, 8.53
2. Golden State, 8.45
3. Toronto, 5.49
4. Oklahoma City, 3.05
5. Cleveland, 2.69
6. Boston, 2.47
7. Utah, 2.46
8. Minnesota, 2.42
9. Philadelphia, 2.05
10. Washington, 1.93
11. San Antonio, 1.79
12. Portland, 1.56
14. Indiana, 0.70
15. New Orleans, 0.57
16. Milwaukee, 0.41
18. Miami, -0.48
This leads to the following championship probabilities for 2018 NBA playoffs.
1. Houston, 39.4%
2. Golden State, 36.5%
3. Toronto, 14.9%
4. Boston, 2.2%
5. Cleveland, 1.9%
6. Philadelphia, 1.6%
7. Oklahoma City, 0.9%
8. Washington, 0.5%
9. Utah, 0.5%
10. Portland, 0.4%
11. Minnesota, 0.3%
12. San Antonio, 0.2%
13. Indiana, 0.2%
14. Milwaukee, 0.2%
15. New Orleans, 0.1%
16. Miami, 0.1%
You can compare the calculations with these implied odds from the markets, taken from Bookmaker on Friday morning, April 13th, 2018.
1. Golden State, 36.6%
2. Houston, 28.9%
3. Cleveland, 10.9%
4. Toronto, 9.1%
5. Philadelphia, 4.8%
6. Oklahoma City, 2.1%
7. Utah, 1.7%
8. Portland, 1.4%
9. San Antonio, 1.2%
10. Boston, 1.0%
11. Indiana, 0.5%
12. Washington, 0.5%
13. Milwaukee, 0.4%
14. Miami, 0.4%
15. Minnesota, 0.3%
16. New Orleans, 0.3%
Houston and Golden State should have the best odds to win the title, and both the calculations and markets agree on this.
My calculations are low on Cleveland. The conventional wisdom is that regular season results don’t matter in predicting how LeBron James will perform in the playoffs. This may or may not be true.
However, LeBron does play almost 4 more minutes per game in the playoffs than in the regular season. This should make Cleveland better in the playoffs. My numbers don’t account for different minute distribution and shows how better models could be built with play by play data.
My calculations are also too high on Boston. I did not exclude games in which Kyrie Irving played in my analysis, so some adjustment should be made for this injury.
Get the game by game predictions each day on the main predictions page.
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