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[Statistical Analysis] Game Coaching Index
Evaluating NBA coaches based on their actual vs. expected records
[Statistical Analysis] Game Coaching Index
Evaluating NBA coaches based on their actual vs. expected records
There was an interesting exchange a few days ago between ESPN.com's Bill Simmons (aka The Sports Guy) and 82games.com regarding Doc Rivers' merits as the Celtics head coach. In his January 12 article, Simmons has Doc on the wrong end of all 8 elements of his "Bad Coaching Index":
Adelman having another bad day.
1. Lousy record in close games
2. Too many turnovers
3. Too many offensive rebounds allowed
4. Not enough winning streaks
5. Opposing 3-point percentage
6. Lousy record on the road
7. Lack of a consistent rotation
8. Downright stupidity
82games.com responded with some detailed statistics on blown leads/comebacks and clutch play, which showed that Boston has indeed blown a lot of leads this season. On the other hand, other aspects of their clutch play this year aren't that bad, and their comeback/blown lead ratio was one of the league's best last year.
I decided to take on this question from a different angle, by attempting to rate NBA coaches on their "game coaching" abilities. Game coaching includes clock management, player matchups, crunch-time play-calling ... a lot of the things that Simmons was complaining about with Doc. To me, the best way to measure this is by evaluating the difference between the number of games a coach's team should win and the number of games they actually win.
In his Basketball on Paper book, Dean Oliver includes a method for calculating a team's expected wins by incorporating their points scored and points allowed into a Pythagorean-like formula. The version that I used for this analysis also appears on ESPN.com's NBA RPI page:
Expected Winning Percentage = Points Scored ^ 16.5 / (Points Scored ^ 16.5 + Points Allowed ^ 16.5)
In the table below, I used this formula to calculate the actual vs. expected career regular season winning percentages for all 30 active NBA coaches (through games of 1/14/06). Once again, thanks to Basketball-Reference.com for providing most of the raw data.
| Actual | Expected | |||||||
| Rank | Coach | Wins | Losses | Pct. | Wins | Losses | Pct. | Difference |
| 1 | Terry Stotts | 71 | 101 | 41.3% | 57 | 115 | 33.1% | 8.1% |
| 2 | Avery Johnson | 43 | 12 | 78.2% | 39 | 16 | 70.9% | 7.3% |
| 3 | Lawrence Frank | 86 | 70 | 55.1% | 78 | 78 | 50.0% | 5.1% |
| 4 | George Karl | 759 | 526 | 59.1% | 700 | 585 | 54.5% | 4.6% |
| 5 | Eddie Jordan | 119 | 177 | 40.2% | 107 | 189 | 36.1% | 4.1% |
| 6 | Maurice Cheeks | 180 | 157 | 53.4% | 173 | 164 | 51.3% | 2.1% |
| 7 | Larry Brown | 1000 | 762 | 56.8% | 976 | 786 | 55.4% | 1.4% |
| 8 | Mike Montgomery | 51 | 67 | 43.2% | 50 | 68 | 42.4% | 0.8% |
| 9 | Nate McMillan | 224 | 207 | 52.0% | 221 | 210 | 51.3% | 0.7% |
| 10 | Flip Saunders | 440 | 331 | 57.1% | 435 | 336 | 56.4% | 0.6% |
| 11 | Scott Skiles | 197 | 184 | 51.7% | 195 | 186 | 51.2% | 0.5% |
| 12 | Mike Woodson | 22 | 95 | 18.8% | 22 | 95 | 18.8% | 0.0% |
| 13 | Mike Dunleavy | 482 | 503 | 48.9% | 483 | 502 | 49.0% | -0.1% |
| 14 | Pat Riley | 1122 | 574 | 66.2% | 1125 | 571 | 66.3% | -0.2% |
| 15 | Mike D'Antoni | 121 | 108 | 52.8% | 122 | 107 | 53.3% | -0.4% |
| 16 | Jeff Van Gundy | 356 | 263 | 57.5% | 363 | 256 | 58.6% | -1.1% |
| 17 | Bob Hill | 259 | 217 | 54.4% | 265 | 211 | 55.7% | -1.3% |
| 18 | Doc Rivers | 230 | 227 | 50.3% | 236 | 221 | 51.6% | -1.3% |
| 19 | Brian Hill | 235 | 248 | 48.7% | 242 | 241 | 50.1% | -1.4% |
| 20 | Phil Jackson | 852 | 333 | 71.9% | 870 | 315 | 73.4% | -1.5% |
| 21 | Rick Carlisle | 225 | 138 | 62.0% | 231 | 132 | 63.6% | -1.7% |
| 22 | Rick Adelman | 722 | 464 | 60.9% | 744 | 442 | 62.7% | -1.9% |
| 23 | Jerry Sloan | 962 | 635 | 60.2% | 994 | 603 | 62.2% | -2.0% |
| 24 | Bernie Bickerstaff | 366 | 433 | 45.8% | 383 | 416 | 47.9% | -2.1% |
| 25 | Mike Fratello | 635 | 507 | 55.6% | 670 | 472 | 58.7% | -3.1% |
| 26 | Byron Scott | 184 | 222 | 45.3% | 197 | 209 | 48.5% | -3.2% |
| 27 | Sam Mitchell | 45 | 73 | 38.1% | 49 | 69 | 41.5% | -3.4% |
| 28 | Gregg Popovich | 483 | 242 | 66.6% | 515 | 210 | 71.0% | -4.4% |
| 29 | Mike Brown | 20 | 14 | 58.8% | 22 | 12 | 64.7% | -5.9% |
| 30 | Dwayne Casey | 17 | 17 | 50.0% | 19 | 15 | 55.9% | -5.9% |
A few notes:
Adelman having another bad day.
- Using this metric, Doc is just below average, losing 4 games that he should have won for his career (including 1 this season).
- Terry Stotts did a great job in his 2 seasons with the Hawks, winning 8 more games than expected over that period. But he's done even better this year with the Bucks, leading what should be a 13-22 team to a 19-16 record.
- With his relatively passive bench demeanor, the fact that Phil Jackson should have won 18 more regular season games over the years isn't too surprising.
- Rick Adelman's relatively low rank isn't much of a surprise, either--after 16 years of coaching in the league, he still looks lost at times on the bench.
Of course, game coaching is just one aspect of an NBA coach's job. More importantly, he is expected to teach, motivate, and implement offensive and defensive schemes to maximize the output of his players. Or, as Simmons puts it:
See, it's not that hard to coach an NBA team. You need nice suits. You need a voice. And you need to keep it simple. Doc Rivers only does two of the three. And that's why he needs to go.
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Posted by jgurney on January 16, 2006 12:36:27 AM PST
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Re: Game Coaching Index
I think any metric which has Gregg Popovich in the bottom 3 can't be any sort of accurate measure. There has to be some sort of diminishing returns towards the positive side of the winning percentage chart - I mean the man is winning 67% of his games.
Comment from Anonymous on January 17, 2006 10:59:41 AM PST
Clearly, Gregg Popovich deserves much of the credit for the Spurs' success over the past decade. He's a fantastic executive, and he has done a great job of motivating his players to buy into his system. But is he a good game coach? I'm not so sure.
Comment from jgurney on January 18, 2006 12:07:26 AM PST
Sing it loud and sing it until the whole Gah-den chants it: "Doc has to go down the river!"
You get one guess as to why the guy hasn't figured out a rotation since he arrived: he doesn't know how to turn good players into better players and make them think like winners!
Did anyone else count the turnovers in game 1? Did you see that Al J did whatever he wanted under the basket and scored, but had the frickin' fastest sprint to fouling out in the whole league in just one night! Oh yeah, Doc, maybe we need to work on foul shots! Duh! And how about knowing what you want your guys to do? Stop wimping out by whining about these professionals needing to "develop."
He makes me sick! His only talent is explaining why the Celts just lost. Was this guy ever on a winning team?
The THE THE Celtics need to clean house of those two bufoons -- Ainge and Rivers -- who have no shame. They dare to laugh when die-hard fans are in agony at their blundering and total ineptness for the game that we used to rule!
Comment from Andy Wiggin from Concord! on November 2, 2006 8:31:54 PM PST
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