Does the NBA betting market undervalue star players when absent? Possibly. Using VORP, an advanced NBA stat, we uncover a potentially profitable ATS trend when the game's most valuable sit out a contest.
Over the last five years, betting markets tend to underestimate the absence of star NBA players to a lineup, making for profitable situations against the spread. Using the league's top players as measured by VORP, an advanced NBA stat derived from box-score statistics that measures player value, bettors can potentially cash-in by fading teams when the season's top performers sit out to rest, injury, or other factors.
Value over replacement player (VORP) is a statistical measurement popularized by baseball sabermetrician and current Cleveland Indians front office employee Keith Woolner. It weighs player production to that of a theoretical “replacement player” representing league averages at key metrics and on a minimum salary. In basketball analytics, it is used specifically as a minutes-weighted counterpart to Daniel Myers' Box Plus-Minus (BPM), which combines elements of box-score information and regression analysis to evaluate a player's quality and contribution to a team in sort of a catch-all number. There are pros and cons to the stat, but it is a useful tool to weigh value, production, and cost both league-wide and over different seasons and bettors can take advantage of it when choosing an NBA pick. Updated VORP can be found at Basketball Reference.
ATS Records and VORP
If bettors blindly faded teams that sat out a player in a game who averaged a 5.0 VORP or better on the season over the last five years, they would have garnered a nearly six percent edge over the books (119-85-2 ATS, 58.3 percent). Here is a look at the season-to-season breakdown of ATS records and margins for each:
*Designates the player put in at least one minute of playing time in every game
There are a few caveats pertaining to the tables above. Firstly, the VORP used is the end-of-season number, not representative of where it ranked at the time of the game. The number doesn't shift too wildly over the course of the season and is likely to still offer an edge. Part of the value embedded in this metric is that players have to qualify in key stats through playing time and specific rate statistic requirements. Secondly, playoff games are included.
As you can see from the data, LeBron James almost single-handedly makes this a potentially profitable venture. Since returning home to Cleveland, the Cavs are 1-17-1 ATS when the King misses a contest. The Spurs were 3-7 ATS last season with Kawhi Leonard out. One of the best two-way players in the league, look for markets to continue to underestimate his absence. VORP doesn't rate defense as effectively as some advanced NBA usage stats, and when great two-way players like James and Leonard, or more defensive-minded players like Marc Gasol and Joakim Noah rated high in the metric, it was a signal the market will undervalue. Something to look for moving forward.