The Importance of Depth

It is commonly accepted that star-caliber players determine success.  Though some teams follow ulterior paths, the majority of NBA teams are constructed around a few high-level players or are in pursuit of those players.  Despite this, roster depth, or a lack thereof, is used as a critical in the analysis of a team.

A large portion of many teams’ successes appears to be based on the contributions of their perceived role players.  In recent seasons, the Denver Nuggets have swarmed opponents with a ten-deep collection of talented players.  The Los Angeles Clippers’ “bench mob” sprinted its way to game-changing runs, while the Spurs seemingly have a continuous collection of players capable of perfectly filling their system.

However, these non-elite players are often dependent on the better players on their roster.  Elite and very good players impact a game in such a way that allows lesser player to increase their production, be it LeBron drawing help defense in the mid-post and finding Shane Battier in the corner, Tony Parker drawing the defensive attention on a pick and roll and setting up Tiago Splitter, or Kevin Garnett patrolling the paint and closing driving lanes allowing Rajon Rondo to aggressively hound opponents and passing lanes (That’s not to suggest that Rondo is not a very good player, just that without Garnett’s incredible defense behind him the value of Rondo’s selective defensive aggressiveness would diminish).

So, how important is roster depth?   In an attempt to display the relative value of roster depth versus “star power”, I ran a linear regression comparing the  total Win Shares of the top X players on a team with that teams net rating, points scored per 100 possessions minus points allowed per 100 possessions, for the 60 rosters of the last two NBA seasons.  Ideally, more data would be gathered.  As the process is relatively simple I will attempt to add further years’ data in the future.

Win Shares are not a perfect indicator of player quality, but serve as a decent proxy (and are easiest to convert excel in team units).  It is worth mentioning that the high r-squared values do not necessarily suggest a high predictive worth for Win Shares.  The defensive win shares formula is largely based on team defensive efficiency, so the likelihood of a relatively high correlation between a group of players’ win shares and that team’s net rating is increased.  Net rating, or efficiency differential, is a better indicator of team quality and a better predictor of future results than team wins, so net rating was used as the dependent variable.

Here are the results the effect of the total win shares of the top 3 players on a team by aggregate win shares on net rating:


For every increase of one total win share, an increase of 0.63 is expected for net rating.

For the top 9 players:


For the top 9 players, an increase of 1 total Win Share adds 0.4 points for net rating.

This table shows the relationship for other groups of players:

Number of Players Increase in Net Rating Per Win Share (slope) R-Squared
Top 3 0.63 0.70
Top 5 0.49 0.77
Top 7 0.43 0.81
Top 9 0.40 0.83
Top 12 0.37 0.81


These results clearly display that as the increase in win shares is spread out over a larger group of players the expected return in net rating diminishes.  This suggests that it is preferable for a teams’ top few players to be better by a unit than a larger group or a single player of lower quality.  To many, this is intuitive.  It is better for your best player to be very good than for a few lesser players to improve.  However, some teams are constructed in such a way that their top one to three players are of lower quality than other teams while the comparison of a larger group is closer.

For a team like the Pelicans who, at least by win shares, lack elite players but have a collection of high quality players, this is a significant dilemma.  Having your aggregate talent spread over a greater amount of players may be less productive for than having that talent concentrated among fewer players.  Fortunately, the Pelicans are in position to “add” elite level players.  Anthony Davis has the potential to be one of the top five players in the NBA, while Jrue Holiday, Eric Gordon, and Tyreke Evans have the skills and athleticism to produce at a higher rate.

The value of top players versus depth likely affected a few key decisions this offseason.  The Golden State Warriors lost bench leaders Jarrett Jack and Carl Landry to free agency, but added Iguodala. Though the departure of Jack and Landry was not specifically prompted by Iguodala’s arrival, the Warriors seem to believe that the value of retaining the depth granted by Jack and Landry did not match the potential of adding a single high caliber player.

The value of talent concentration versus depth is one of the several questions facing NBA front offices, and an issue the Pelicans will surely address several times in the near future.

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