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Posts Tagged ‘Replacement Efficiency

Stats Tuesday: Should “replacement efficiency” be used instead of league average efficiency, in NBA comparisons?

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Derrick Rose at a promotional appearance.

The value of Derrick Rose’s efficiency in his MVP season is questioned by the advanced stats community (Photo credit: Wikipedia)

A hot topic among basketball nerds is what to do with players who shoot either a league average efficiency or a below average one. Our instincts tell us a player who shoots an average shooting efficiency when he has teammates who’s efficiency is well above average, is a problem. Because it indicates the player could be passing the ball more to these more efficient players, thus raising his team’s efficiency. It indicates that if the team’s efficiency is above league average, that the credit for this should be relegated to the players taking above average shots in efficiency, not the one taking a ton of possession at an average efficiency that doesn’t move the meter.

To use an example, in the last non-lockout year (2010-2011) league average True Shooting Percentage/TS% (incorporating 3s and FTs, essentially creating a points per shot metric) was .542. The MVP, Derrick Rose, had a TS% of .550. Kobe Bryant’s score was .548, Carmelo Anthony’s .557. They are considered superstar scorers in this season because of their volume points per game. But using a strict model of comparing volume and efficiency can create some shocking results. Take the two examples of Tyson Chandler and Nene, both not known for scoring talent, but among the league leaders in efficiency in 2010-2011. Chandler takes 7.26 shots a game in the regular season on the Mavericks (using the calculation FGA + 0.44*FTA) at .697 TS%. Multiplying Chandler’s volume of shots (7.26) times league average efficiency for points per shot (.542 TS%) adds up to 3.94 points. At Chandler’s real efficiency (.697) he scores 5.06 points, for a margin of approximately +1.12 points from average. Nene likewise has 11.1 shots at .657 TS%, using the same calculation as with Chandler he ends up adding +1.27 points compared to what his shots taken at average efficiency would create. However look at what happens when the same calculation is done with Rose, Melo and Bryant. Rose, taking 22.74 shots would create 12.3 points if had shot at league average efficiency, while at his real efficiency of .55, creates 12.5 points, a whopping difference of +0.2 in the points column. Carmelo, using 22.98 shots a game at .557 TS%, using the same calculation ends up adding about +0.35 pts compared to if those shots had been taken at an league average level, while Bryant at 23.1 shots converted at .548 TS%, ends up adding a measly +.14 points compared to the average conversion of those shots. All 3 of Rose, Melo and Bryant’s scores not only trail Chandler and Nene’s numbers, but they’re not even in the same ballpark.

This is why statistical attempts to quantify scoring have met such difficulty. Read the rest of this entry »

Written by jr.

October 9, 2012 at 10:32 am