Archive for the 'Analysis' Category

Here are some quick logistic regressions I ran between offensive/defensive efficiency (as measured by my 1951-2010 estimation equation) and whether or not a team won a championship...

The first regression is between regular-season offensive/defensive rating (relative to the league average) and championships won since 1951, the first year for which I can estimate possessions. The logistic equation to predict championship probability from RS efficiencies was:

p(C) ~ 1 / (1 + EXP(4.7267572 - (0.3988116 * Offense) + (0.612137 * Defense)))

From this equation, we would expect an average team during the Regular Season (0.0 on offense & defense) to have a 0.9% chance of winning an NBA title. If you increase offense to the following levels while keeping defense average, you see this pattern:

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See also: #21-25, #26-31

Note: This post was originally published at College Basketball at Sports-Reference, S-R's new College Hoops site, so when you're done reading, go over and check it out!

20. Wake Forest Demon Deacons (+12.87 SRS)

Record: 586-365 (.616)
Prominent Coaches: Carl Tacy, Dave Odom, Skip Prosser
Best NCAA Finish: Lost Regional Final (1984, 1996)

Perhaps better known for what their alums do after leaving the program (Billy Packer, Muggsy Bogues, Tim Duncan, Chris Paul, etc.), Wake nonetheless has maintained a near-perennial NCAA Tournament presence (and a frequent top-4 ACC team) over the past 3+ decades. Carl Tacy's teams were very good (AP top-20 three times) in the first half of the eighties, and following a short, mediocre stint under Bob Staak from 86-89, Dave Odom took the reins and oversaw one of the most successful periods in school history (including the recruitment of the greatest Deacon of all, Tim Duncan). Under Odom, WF had 7 consecutive NCAA berths, but the last in that run was the most disappointing -- after climbing as high as #2 in the AP poll, Wake was unceremoniously bounced by Stanford in the 2nd round, ending Duncan's collegiate career. After Odom left for South Carolina in 2001, the late Skip Prosser continued a winning tradition with 4 straight Tourney appearances and the development of Paul, before tragically passing away in 2007. Today, the Deacs hope to rebound from Dino Gaudio's up-and-down tenure with the hiring of Jeff Bzdelik in 2010.

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By popular demand, here's a sequel to the post I wrote on Friday, which focused on the NBA players who played for the best offenses over the course of their careers. This time I'll be looking at the players who were a part of the best defenses in their careers, but the methodology remains the same:

1. Estimate defensive efficiency (points allowed per 100 possessions) for every team since 1951 in the regular-season and playoffs.
2. Adjust playoff defensive ratings up/down based on regular-season offensive strength of postseason foes.
3. Compare defensive efficiencies to the league average (to account for the fact that the avg. was, for instance, 85 pts/100 poss in 1951 and 108 in 2010)
4. Find career averages (weighted by MP with each team) for every player since the NBA started tracking minutes in 1952.

Make sense? Good. Here are the all-time players who had a presence on the best defensive teams (minimum 15,000 career MP):

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Back in June, right before the Finals tipped off, I developed a method to estimate possessions for teams going back to 1951 using the following regression equation:

Possessions ~ -4.05*Wins - 3.96*Losses + 0.97*FG + 0.75*FGA + 0.70*FTA - 1.37*OReb + 0.53*TotReb + 0.31*Fouls - 0.50*Points +0.19*Opp. Pts

For most teams, this method can estimate a team's actual possessions total within roughly one possession per game, so it's surprisingly accurate given the basic nature of the inputs.

At any rate, I went on to use this method in finding the most similar NBA Finals matchups to the Lakers/Celtics clash, as well as in determining the Finalists that improved the most during the playoffs, and ranking playoff defensive performances. Today, though, I want to use estimated offensive ratings as a way to rank the players who have played for the best offenses during their careers.

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Last October, Jason Lisk published two great studies at PFR about which passing stats are the most situation-independent, looking at the year-to-year correlations in rate stats for both QBs that changed teams & teams that changed QBs. (Chase Stuart followed this up with additional interception rate research in March.) His conclusions? Sacks per dropback and completion % were the most consistent, which implies that those are more under the control of the individual QB rather than the situation he's in. At the other end of the spectrum, interception % is actually the least consistent rate stat, indicating that interceptions (or lack thereof) are more due to luck and situation than actual player skill (a finding Chase reinforces in this Footballguys article). This also means that when evaluating QBs, we should regress their interception rates more to the mean than their sack or completion rates.

What does all of this have to do with basketball? Well, I decided to do the exact same study for NBA players, except instead of looking at players who changed teams, I looked for players whose offensive roles changed (as measured by possession usage %). I can certainly look at players who changed teams as well, but for basketball my hypothesis is that the player's role is as important as anything in determining certain rate stats. This goes back to the concept of "skill curves", or the idea that a player's efficiency is fundamentally a function of not only his own skill, but also his usage rate.

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There are a lot of attributes that I've looked into as the hallmarks of great teams, including dominant wins, ideal usage allocations, and superior playoff point differentials. But here's another characteristic to throw onto that heap -- season-long performance vs. playoff teams.

Since the playoffs only feature the league's best teams -- a.k.a. those through which the path to a championship runs -- you could argue that we should judge a good team's ability by its performance vs. fellow postseason participants. Or at least that's the premise here: for every season since 2000, I whittled down the NBA schedule (regular-season and playoffs) to just include games between 2 playoff teams. Then I ran the Simple Rating System formula on those games, adjusting for a home-court advantage of 3.3 PPG and setting the results relative to the overall league average of 0.0 (to keep things on the familiar SRS scale).

The results are the teams that performed the best vs. playoff teams during the year in question:

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When Scottie Pippen, Dennis Johnson, Karl Malone, & Gus Johnson get enshrined into the Naismith Memorial Basketball Hall of Fame this evening, it will represent not only the culmination of a lifetime's hard work and dedication by four great players -- it will also establish the greatest collection of winners to ever enter the HoF at once.

Or at least, according to my calculations it will. Recall that in posts like this, I estimated the W-L record of a player's team when he played thusly:

"...take the team's winning percentage in all games ... and multiply by the player's games played for wins, then subtract that from his games for losses."

It's a kludge, I admit, but in the absence of pre-1991 playoff gamelogs, it's the best we can do -- and it's not too inaccurate for such a simple solution. Anyway, according to that method (and combining regular-season + postseason wins), Malone, Pippen, & D.J. are all among the 20 winningest NBA players to ever lace up a pair of sneakers:

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Today I thought we'd briefly put aside the top college programs series and take a look at the NBA teams that had the most personnel turnover from one season to the next. As we all know, the 2010-11 Miami Heat will probably return less than half of their minutes from a year ago, with the top newcomers by playing time expected to be LeBron James & Chris Bosh. How does this stack up against teams that had a lot of roster turnover in the past? Here are the (non-expansion) clubs since 1965 who gave the smallest % of their minutes to players who had been on the roster the previous season:

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See also: Part I

Note: This post was originally published at College Basketball at Sports-Reference, S-R's new College Hoops site, so when you're done reading, go over and check it out!

25. Ohio State Buckeyes (+12.29 SRS)

Record: 522-337
Prominent Coaches: Eldon Miller, Jim O'Brien, Thad Matta
Best NCAA Finish: Lost National Final (2007)

Columbus, OH will always be a football town first and foremost, but the Bucks' basketball team has also been deceptively competitive over the past 31 years. Under Eldon Miller & future Maryland coach Gary Williams in the 1980s, Ohio St. was frequently among the top 30 teams in the country, though they could never quite recapture the form of their 1980 team (Herb Williams, Kelvin Ransey, & Clark Kellogg led OSU to the Regional Semis & the 4th-best SRS in the country). That changed during the early years of Randy Ayers' tenure, when they went 53-10 in '91 + '92 en route to 2 Big Ten crowns and a Final Four near-miss in 1992. But after 1992 UPI POY Jim Jackson left school, OSU slipped badly, bottoming out at 6-22 in 1995. Ayers was then replaced by Jim O'Brien, who resuscitated the program and took them to a Final Four in just his 2nd year at the helm. From '99-02, O'Brien's Buckeyes had their most successful 4-year run since the early 1960s, although revelations about recruiting misdeeds cost him his job and forced the Buckeyes to vacate more than 3 years worth of results. Luckily, though, former Xavier coach Thad Matta was hired to pick up the pieces and he has simply led OSU to the best 6-year run in their history, solidifying their place on this list with 4 NCAA berths in the last 5 years (including a Championship Game appearance in '07).

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Note: This post was originally published at College Basketball at Sports-Reference, S-R's new College Hoops site, so when you're done reading, go over and check it out!

With the addition of 2010 stats to the site about a month ago, CBB at SR now has game-by-game results for each of the past 31 seasons (1980-2010). This means that we can calculate our signature team power-ranking statistic -- the Simple Rating System (SRS) -- for every team in that span, estimating a team's "true" strength by adjusting point differential for strength of schedule. Armed with those ratings, I went back and found the average SRS for each program over the past 31 seasons; this post is the first in a ranking of the top 31 programs by that average. The only rule for qualification: teams who didn't play all 31 seasons in D-IA were not eligible (sorry, Miami, Missouri St., & Tulane). Other than that, it's all about having the highest average SRS since 1980. To the rankings...

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