Archive for the 'Statgeekery' Category

Among the players in their most common lineup, which teams divvy up possession usage most efficiently?

To answer that question, let's use a method I introduced here. Just like that old post, this one is going to lean heavily on the concept of "skill curves", which says that a player's offensive efficiency drops as he shoulders more and more of a team's possessions. I realize this isn't always the case for all players -- but as a very general rule it holds, so let's pretend for a moment that this simple model does in fact explain the fundamental usage-efficiency tradeoff in basketball. Under those rules, a player using 18% (or fewer) of team possessions while on the court would see his efficiency change by 1.65 points of offensive rating for every 1% change in usage, a player using 18-23% would see a change of 1.24 pts of ORtg for every 1% of usage change, and a player using 23% or more would see a change of 0.82 pts per 1% change in usage.

To find every team's most common lineup, I gathered data from 82games.com, and scaled the sum of those players' season-long possession usages to equal 100%. I found their predicted lineup efficiency based on actual ORtgs and usage patterns, and also found the optimal distribution of possessions that would maximize offensive efficiency according to the rules above. The teams with the smallest difference between their actual usage pattern and the optimal pattern can be considered to be efficiently allocating their possessions.

Here are the teams, sorted by the squared difference between their actual and optimal usage patterns:

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Here's what you get when you run the BBR Rankings (and our old friend Maximum Likelihood) on every game, regular-season & playoff, that took place in the calendar year of 2010:

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2010-11 NBA power rankings through the games played on December 30, 2010:

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I was browsing the stats this morning when I noticed that Ron Artest is currently using 14.7% of the Lakers' possessions when he's on the court, the 19th-lowest possession-usage rate of any qualified player in the NBA. Before joining L.A., Artest was accustomed to usage rates well over the league average of 20%, which had me wondering how Artest's decline in usage compares to other players who changed roles at varying times in the their careers.

It turns out that Artest is currently on pace to be one of only 5 players in NBA history (since 1952, at least) to have one qualified season with a possession rate of at least 25% and another with a rate of 15% of less:

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In honor of the Christmas Day games tomorrow, here are some great Christmas performances from the past. First, the best individual games (from 1986-2009) according to "APMVAL", the adjusted plus/minus-based game score metric I introduced here:

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2010-11 NBA power rankings through the games played on December 23, 2010:

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You'd better read this post from August if you haven't yet.

In it, I looked at the year-to-year correlation coefficients for various offensive rate stats (TS%, AST Rate, TOV Rate, FTA/FGA, & OReb%) when a player changed his role in the offense. Essentially, I concluded that offensive rebounding and assists are relatively immune to changes in a player's possession usage, foul-drawing & turnover avoidance are less immune, and scoring efficiency is the most prone to fluctuate with a role change.

Today I wanted to expand on that post by adding another variable into the mix: changing teams. Other than the new variable, though, this study's format is basically the same as in the first post -- except I used touches per minute rather than possession % to define a player's role, and I added Dean Oliver's Offensive Rating (ORtg) into the mix.

Here's the setup: Once again, I found every player from 1974-2010 who was between 24 and 34 years old and played at least 1,000 minutes in back-to-back seasons. I then sorted those players by the absolute change in their touches/min, and took the top quartile as my sample of players who changed roles. I also isolated players who played for a different team than they had the previous season, forming four groups: players who changed team & role; players who changed role only; players who changed team only; and players who changed neither team nor role. Finally, I ran correlation coefficients on the year-to-year offensive rate stat performances for each group:

The results:

• Shooting/offensive efficiency is actually far more impacted when a player changes teams than when he changes roles. This suggests that a team's system, coaching effects, and teammate interactions play a much bigger role in determining shooting percentages than "skill curve" effects.
• Assists are more dependent on role than team -- for obvious reasons, how much you have the ball in your hands is a major factor when it comes to how often you set up your teammates.
• Turnovers, fouls drawn, and offensive rebounds are all more team-dependent than role-dependent, but the differences are nowhere near as drastic as those observed in shooting efficiency or assists.
• For players with no major contextual changes, assists and offensive rebounds are relatively stable; foul-drawing and turnover avoidance are less consistent; and scoring efficiency is the least consistent of all. This mirrors the findings of the original study.
• Finally, it bears mentioning that even at its least consistent (TS% for players who changed teams), NBA player performance is way more predictable than that of the NFL quarterbacks Jason Lisk looked at in the football study that inspired these posts.

2010-11 NBA power rankings through the games played on December 16, 2010:

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Tyrus Thomas is in some pretty heady company this season:

(For single seasons; played in the NBA/BAA; in the regular season; in 2010-11; requiring Offensive Rating >= 110 and Usage Pct >= 26 and Defensive Rating <= 101 and Minutes Played >= 450; sorted by descending Win Shares Per 48 Minutes.)

Now, the defensive rating might overstate Thomas' case (although the Bobcats are 4 pts/100 poss. better on D when he's in the game), but even if you remove the defensive rating requirement, he's still in a good group:

I'll also grant that Thomas is the only non-starter in the group, meaning the lineups he's faced have not been as strong as the others on that list.

Still, that's impressive production thus far... Thomas flies under the radar because he always seems to come off the bench for mediocre teams, but he's quietly having a strong season. With BBR Blog favorite Gerald Wallace slumping and suffering an ankle injury this week, Thomas now has a chance to show everyone what he can do in expanded minutes.

Although we're only a month and a half into the season, the 2010-11 campaign has already seen its share of impressive winning streaks. The Spurs rattled off 12 straight across almost the entire month of November (a streak matched by the Mavericks last week), the Lakers & Hornets each won 8 consecutive to start the year, and the Celtics, Heat, & Knicks are currently in the midst of 8+ game win streaks themselves. How probable have these runs of victories been?

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