Win probability for the 2018 NBA Finals

For the 2018 playoffs, I’ve been using data from game results and markets and then filtering to attempt to account for injuries. More details below.

For the 2018 NBA Finals, my model says that Golden State is better than Cleveland by 6.2 points on a neutral court. This leads to the following odds for the series.

Golden State has a 89.6 percent chance of winning the series.

As of Tuesday afternoon on May 29th, 2018, Bookmaker had Golden State -1100 to win the series (Cleveland is +750). This implies a 88.6% chance to win the series for Golden State once you account for the vig.

I’m really surprised the numbers match up so well. The NBA playoffs have been frustrating to predict from a numbers perspective because of injuries and Golden State’s underachieving. Here’s how my model works.

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 38 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. It also assumes Cleveland’s Kevin Love will play. 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.

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. Golden State, 8.89
2. Houston, 8.11
3. Toronto, 4.59
4. Cleveland, 2.72
5. Philadelphia, 2.32
6. Oklahoma City, 2.17
7. Utah, 2.10
8. Boston, 1.44
9. San Antonio, 1.35
10. Minnesota, 1.26
11. Washington, 1.26
12. Portland, 0.79
13. Indiana, 0.70
14. New Orleans, 0.69
15. Milwaukee, 0.28
16. Denver, 0.26
17. Los Angeles Clippers, -0.60
18. Miami, -1.23
19. Charlotte, -1.39
20. Detroit, -1.46
21. Dallas, -2.71
22. Los Angeles Lakers, -3.68
23. Memphis, -4.27
24. New York, -4.51
25. Orlando, -4.73
26. Brooklyn, -5.14
27. Chicago, -5.44
28. Atlanta, -5.50
29. Phoenix, -6.67
30. Sacramento, -7.35

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