Saturday, December 1, 2012

Today's Games now available for the NBA

Now that the NBA rankings are up and running, I can now relaunch the Today's Games feature of this site.  Here is a description of what this feature is intended to do (you can also see here for additional background).

Today's Games

The main purpose of this feature is to highlight "unexpected" point spreads and over/unders for games to be played that day.  I can calculate expected point spreads and over/unders using my betting market rankings (see the Methodology page for a description of how the rankings are derived, and see the end of this post for how to use the rankings).

Each morning, I can then compare the "expected" point spread to the actual point spread.  What I've found is that large misses (greater than 2 points) are often a good indication of key starters missing from the lineup.  So, one could use this feature as a supplement to a stat-based model, or as a general handicapping tool.  Big misses in the expected point spread are indications that something abnormal has happened, and that it may be best to lay off (or you could use the miss itself as a correction factor in your projection).

Here is an example of how this feature can be used:

How Much is Rondo Worth?

Here is a sample from today's table (December 1, 2012):


As you can see, the biggest miss is on the Celtics-Bucks game where the Bucks were favored by 2.3 points more than what my rankings predicted.  The most likely explanation for the miss is Rajon Rondo's absence, who is serving the second game of a two game suspension (this is consistent with the point spread from the previous night's game against the Trailblazers where the miss was also 2.3 points).

So, one way to interpret this result is that the market values Rondo at about 2.5 points per game.  This actually seems a bit low, but is roughly consistent with Rondo's two year adjusted plus/minus of 3.4 points.

How to Calculate Points Spreads and Over/Unders

Here is how the rankings are used to calculate expected point spreads and over/unders:
  • Point Spread (in favor of home team) = HCA  + (B2Bhome - B2Baway) + (GPFhome - GPFaway)
  • Over/Under = 2*APS + (oGPFhome + oGPFaway - dGPFhome - dGPFaway)
where:
  • League Average Points Scored (APS): 97.0 points (recalculated daily)
  • Home Court Advantage (HCA): 3.25 points
  • Back to Back Penalty (B2B): -1.25 points (see here)

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