Developing a Rating System for SOM Hoops

by Dave Little


Defense Ratings

One-on-one defense

The defense card is divided into 31 separate chances (numbered 21-51) represented equally in the action deck. The defender card will be accessed on 40% of possessions, for an estimated 8 times per position per game. Each result, then, will be encountered 8/31= 0.26 times per game.

The values for each result are assigned as follows:

Steal = +2 (takes away a possession from opponent; gains possession for team)
Turnover = +2 (Ditto)
Foul = (-1) (arbitrary)

The value of the defense portion of the card:

0.26 * (2S+2T-F)

Example: Charles Barkley

7 Steals, 2 Turnovers, 1 Foul = 0.26 * (14+4-1) = 4.42

Other Players: Laettner 0.52; Blaylock 9.36; Stockton 5.2

X-column defense

The X-column defense comes into play on 1/6 of the opponents' shot attempts. Since the results of the X-column readings represent opponents' shots made, the ratings will be expressed as NEGATIVE numbers. On the assumption that each position will face 20 shots per game, each player's X-column will be accessed 3.33 times per game. Each X-result costs the team a basket (2 points). Note that shot-blocks on the X-column affect the game results in the same way that missed shots do; therefore, no bonus is awarded for shot-blocks generated from the X-column.

The individual X-columns are accessed in proportion to the shots faced. I have arbitrarily assigned the following modifiers:

Guards/RF - O=2, P=1.33, I=0.166
(A 60/40 split of O/P with a small addition of I-column for the occasional switch)

Center/LF - I=2.66 (80%), O=.33 (10%), P=.33 (10%)

The formula becomes :


Points allowed = 2 * [(2* O%) + (1.33*P%) + (0.16*I%)]


Points= 2 * [(2.66* I%) + (0.33* O%) + (0.33* P%)]

Example: Charles Barkley (LF)

I%= 0.333; O%= 0.333; P%= 0.667

Points= 2 * [(2.66*0.333) + (0.33*0.333) + (0.33*0.667)] = 2.44 points per game allowed

Other players: Laettner 2.44; Blaylock 1.54; Stockton 1.59

Fast-Break X-column defense

The X-column defense readings for the FB shots are resolved in the same fashion as the other X-column shots. There is a different distribution of readings, since the action deck assigns a defender with each fast-break. Assuming 30 fast-breaks per game (as previously), the defenders will distribute as follows: RG 8.5, LG 8, RF 7.5, LF 3, C 3. Divide each of these figures by 6 (the proportion of shots which will lead to X-column results), and multiply by 2 points per basket allowed to get the final position modifiers:

RG 2.83; LG 2.64; RF 2.5; LF 1.0; C 1.0

The formula becomes:

Position Modifier * FBX%

Example: Charles Barkley (LF)

Points allowed= 1.0 * 0.667 = 0.667 ppg allowed

Other players: Laettner 0.5; Blaylock 0; Stockton 0

Shot-Block Ratings

The shot-block ratings from the player card are based upon a 20-point scale, and are accessed from the Team Defense card on a die roll of 7 in the Inside and Penetrate columns. Failure to block the shot under these circumstances results in a basket; therefore, blocks are worth 2 points. A rough estimate of shots taken is 20 per position. 80% of shots from inside players are inside shots, totaling 32 per game. 40% of shots from outside players are Penetration shots, totaling 24 per game. Therefore, 32+24=56 shots are included. One-third (2/6) will fall on the Team Defense card, totaling 18.67. One-sixth of these results will be a die roll of 7. Therefore, the shot-block rating will be accessed 3.11 times per game, giving the shot-blocker an opportunity to prevent 6.22 points.

The formula is simple:

Block Bonus = 6.22 * Block %

Example: Charles Barkley

Block Rating = 4 (20%)

6.22 * 0.2 = 1.24 points prevented per game.

Other players: Laettner 1.87; Blaylock 0; Stockton 0

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