The heavy rigours of the NBA season manifest themselves in numerous ways that could impact your fantasy team. The 2009 campaign will provide fantasy owners with the decision to draft many high-quality players, but should managers be concerned about the Rookie Wall?
The phenomenon often described as 'a Rookie Wall', is based on the concern that the regular NBA season will likely be the most intense series of games that basketball players have faced as they enter their rookie NBA campaign, and players often blame their fatigue when explaining the occasional off-night.
I wasn’t sure what to expect going into this analysis–my initial instincts were expecting a slight dip in rookie stats for March and April. But, after compiling some data, I found that the fantasy value of rookies over the past few seasons seems to defy the notion of a Rookie Wall.
Hopefully after reading this article, you will recognize that on average, the Rookie Wall will not dampen your team effectiveness near the end of the fantasy season.
My analysis employs the Linear Weights PER by Zach Fein. For those who are not familiar with the PER or the Linear Weights PER metrics, here is a quick explanation of how the value is used and calculated.
John Hollinger has developed a formula that calculates one statistical number dubbed the Player Efficiency Rating (PER) in order to facilitate player comparisons. The PER is more complicated than the quarterback efficiency rating, and the PER is much more complicated than the simple OPS or WHIP metrics in the MLB.
Unfortunately, Hollinger’s model is difficult to use, because the true PER must be normalized with overall team statistics since individual teams have different per-minute potential due to the pace of their games.
Zach Fein simplified Hollinger’s Player Efficiency Rating by creating a predicative formulaic model that relies only on common box score statistics. Fein identified mathematical constants to weight the statistical categories and calls the formula the Limited Weights PER (lwtsPER).
This revised metric loses the weighting for team pace, but should be valid for comparing a single player’s PER as they play on one team. Fein’s method is similar to Hollinger’s alternate statistic known as the Game Score formula. But, the lwtsPER is more useful for my analysis since Fein’s method allows me to compare the per-minute effectiveness while the Game Score formula only gauges the absolute performance of the total game.
I utilized Fein’s approach to find the lwtsPER value for my rookie stats to compare the month to month values. If a 'Rookie Wall' were to exist, we would expect my rookie sample to have had experienced lower lwtsPER values as they near the end of the season.
Before I dive into the analysis, keep in mind that few NBA teams are willing to use rookies in a consistent role from the opening weeks through to the season finale. Instead, rookies usually experience an evolving role on their team over the course of the season.
The 2008-2009 Season was rare with quite a few rookies logging consistent minutes and receiving offensive plays right out of the chute. I wanted to identify a possible impact attributed solely due to fatigue, so I assembled a truncated list of month by month rookie stats. My list only includes recent players that had consistent playing time and team roles during their rookie campaign.
Players like Rudy Gay, Deron Williams, Russell Westbrook, and Randy Foye are excluded since their minutes per game and role changed drastically midway through their rookie campaign. Their coaching-induced changes to their playing time would show statistical improvement as they progressed through the season.
In addition, players such as Brandon Roy are excluded since they missed a significant number of games during their rookie seasons, so they might have avoided a Rookie Wall with DNPs during the middle of the season.
Even though Michael Beasley began the season as a starter and later moved to the bench, I included him in this analysis because his playing time and role remained mostly constant.
However, I withheld his April production since he closed out the season with a handful of incredible games as a starter, and I felt the outlier games could misrepresent his PER trend versus the regular season. Adam Morrison also had a similar role as a starter or bench player, so his stats seem useful for analysis.
Last, I included Bargnani (with the exception of his one-game in April) to show his production leading up to his Mid-March injury. Bargnani had played in over 60 games off the bench, which means the Rookie Wall could have negatively impacted his February or March statistics.
Click here to download a lwtsPER summary of the month-over month split stats for OJ Mayo, Derrick Rose, Michael Beasley, Mario Chalmers, Kevin Durant, Al Horford, Adam Morrison, Andrea Bargnani, Marvin Williams, and Chris Paul
Here are some general observations of the data. First, most players saw rather consistent lwtsPER production during the season with no player becoming extremely ineffective in March and April.
Second, Chris Paul and OJ Mayo are the only players that experienced a 20% or greater month-over-month decline in their PER during February, March, or April (the months we would expect the rookie wall to become a factor).
Third, most of these rookies continued to improve their estimated PER as the season progressed, which would indicate that their positive ability for growth was a greater factor than the negative of hitting a Rookie Wall.
The Trend Slope identifies the slope of a linear regression trend line for each player’s PER from November to April. The trend line represents a statistically derived best-fit straight line through the rookie’s monthly lwtsPER.
A positive trend line slope means we would expect improvement to the lwtsPER as time progressed; while a negative slope means that we expect worse performance as time progressed. Of these 10 rookies, only OJ Mayo has results where a regression line would indicate a decline of performance as the season progressed.
Mayo played the third-highest minutes of any NBA player last season, and the extremely high workload might have caught up with him. However, even with these observed factors, few would conclude that Mayo became outright unproductive in terms of fantasy performance during March and April.
All rookies will struggle since they face a stiff learning curve, and they are introduced to high-caliber competition. As a result fantasy managers have many factors to consider when drafting rookies.
However, it seems reasonable to exclude the rookie wall as a deterrent. Talented rookies will likely get better as the season winds down; they will not get significantly worse due to fatigue.
If you believe Blake Griffin, Brandon Jennings, Tyreke Evans, or James Harden have what it takes to produce in the NBA, then they’ll have value (barring serious injury) for your fantasy team all the way through the fantasy playoffs.