APBRmetrics

[Eli W]

I decided to start a separate thread on this so as not to take over the discussion of updates at Basketball-Reference.

[asimpkins]

Yes, their assist measures are certainly measuring two different things. In an ideal world, I'd like both of them to be offered, but if I can only have one then I think Pomeroy's answers a more important question.

My suggestion would be to keep Hollinger's Assist Rate also -- which shows what a player is likely to do when get gets the ball -- and group it together with a bunch of similar rates: how likely is he to go to the foul line? to shoot a three? to turn it over? etc. You could get as detailed as you like with this.

As for usage and turnover. My impression was that the difference was that Pomeroy's percentages didn't count assists as using a possession -- only shooting, free throws, or turnovers. This keeps everything neat because you can't have two people, the shooter and passer, credited for using the same possession.

Again, just an alternate way of doing things, but I like it a bit more because of the dubious natures of assists. Again, I'd be all for expanding the Advanced Stats page to another table and offering more instead of less.

[Neil Paine]

Yeah, I should say that only "usage" and "TO rate" are technically trying to measure the same thing -- although both "assist rates" are trying to tell you about passing tendencies for a player. But even if you used the Hollinger concept for assist rate (Ast/Poss), you need a better possessions estimator in the denominator. What Hollinger does in all three of his rates is apply some variation on the team possession formula to individual players (and for usage it's not even the proper formula, he multiplies assists by 1/3 to "avoid overvaluing PGs"), which is entirely inappropriate. In the denominator, we need actual individual possessions, which is why Ken is correct to use Dean's formula from BoP. (Incidentally, that formula does include assists as a partial possession consumed, but it splits out possession credit between the passer and the shooter.)

As for assist ratio, don't you think that the % of teammate FG a player assists while on the floor is a better indicator of passing than the % of his own possessions he devoted to assists? Both speak to tendencies, but the latter says much less about "passing skill". You can devote a large % of your poss to assists and still be a bad passer if you never shoot and never do anything with the ball. However, under Ken's definition, you have to be actively engaged in the offense as a passer to score highly. To me, that definition says a lot more about passing than Hollinger's.

[Neil Paine]

Oh, and Re: ASimpkins - I, too, would rather see the KenPom definitions, but coupled with tendency stats like Bob Chaikin's touches. Bob breaks down touches per minute, along with the percentage of touches devoted to shooting, passing, drawing fouls, and committing turnovers. Adding those under advanced stats would allow us to retain the superior passing metric (KenPom's "Assist Rate") while also giving us information on player tendencies (like John's "Assist Rate" does). I know that, roughly, Touches = FGA + TO + (Ast/0.17) + (FTA/1.15). The 1.15 comes from the league FTA/PF, but I don't know how the 0.17 is derived. If we can get the formula straight, it would probably solve this dilemma for everyone.

[kjb]

I like to use an adjusted Hollinger usage stat. One thing that has bugged me about his Usage is that it doesn't add up to the team totals. If you multiply Hollinger's basic formula by .82 totals from individual players will then add up to a total very close to their team total. In my opinion, that's a better approach than talking about a player's usage at rates much higher than the team's possession total.

Hollinger's Usage sorta gets at plays, but not when it includes assists. Unless you're going to put in a deflator for assisted FGs.

[Carlos]

davis21wylie2121 said

[Eli W]

[Neil Paine]

I'm opposed to Hollinger's and not BobC's because Bob never claims that his touches breakdown is measuring anything but tendencies. On the other hand, Hollinger openly uses his formula to measure passing skill, when in fact it's nothing but a measure of passing tendency. I also like the fact that BobC's method can tell you what a player does with all of his touches (the only options are shoot, get fouled, pass, or turn it over).

I was thinking about an ideal "assist rate," though, and you are right when you say:

[Neil Paine]

[Eli W]

[bchaikin]

for what it's worth i've been charting cavs games this season (i'm in cleveland) and counting touches for lebron james in particular since you know he'll be seeing the ball alot on offense. for example in the CLE/NYK game of 11/2/07 james played 44 minutes and got 95 touches, threw 53 passes, got fouled 14 times, took 28 shots, and committed 2 turnovers. 53 + 14 + 28 + 2 = 97, but he got fouled twice in the act of shooting and hit the shot (i.e. got fouled 1 time and had 1 FGA but just 1 touch). with his 53 passes he got 7 assists...

but in the CLE/DAL game of 10/31/07 in 36 minutes james got 64 touches, threw 43 passes, took 11 shots, got fouled 5 times, and committed 5 turnovers (2 of which were offensive fouls). 43 + 11 + 5 + 5 = 64. but with those 43 passes he got only 4 assists...

if you pick one or two players in a game (that you know will get alot of touches) it's easy to get an idea of their tendencies once you log a number of games. i also charted eddy curry in the CLE/NYK game and in 33 minutes he got 26 touches, with 16 shots, he got fouled 5 times, committed 1 turnover (low for him), but he threw just 4 passes (got 1 assist), one of which was actually a handoff more than a pass and thus really never had a chance to be an assist...

i tend to only count passes that i think have a chance to be an assist (even frontcourt passes on out of bounds plays), i think to myself had the player receiving the pass immediately shot and scored would the passer have been credited with an assist. thus passes in the backcourt when a team brings the ball up the floor when there are no defenders around i don't count as "passes", nor do i usually count a handoff of the ball as a pass...

you do this enough and you'll come up with good approximations for calculating player touches...

[Kevin Pelton]

My perspective is that to relate usage as quantified to the conceptual definition of usage we generally have, it makes more sense to entirely throw out assists and offensive rebounds and use the play definition instead of the possession definition.

That means using simply FGA + (.44*FTA) + TO divided by the same measures at the team level.

[jkubatko]

[Kevin Pelton]

Yep. The nice thing about that in terms of Turnover% is you can know that TO% plus FTA% plus FGA% add to 100.

[gabefarkas]

The thing is, you aren't considering everything that a player does to impact the game. You're just considering shot attempts and turnovers. Most of the time when a player has the ball in his hands, he passes it (or attempts to pass it, resulting in a turnover). Those passes/attempted-passes lead to either turnovers, assists, or nothing.

If you include assists in the measurement, it allows you to consider everything a player does with the ball, including "nothing". Using the literal definition of the word "possession" (instead of the basketball definition), you could calculate:
100 = Assist% + TO% + FGA% + FTA%