Threes And Assists

by Blake Murphy 30. October 2012 22:18

One of my biggest complaints with basketball box score statistics is that I find assists to be an unfair measure of someone’s passing performance.

Growing up as a hockey player, nothing infuriated me more than making a great play and a nifty pass only to have a teammate whiff or hit the goalie in the chest, robbing me of an assist.

In basketball, it’s much the same, where a player can draw a double team and kick out to an open three-point shooter and have them throw up a brick. Or worse, they can feed a dive-man off a well-crafted pick-and-roll, only to have that player fouled, giving the player and team two points but the passer nothing in the box score.

Of course, stats shouldn’t mean much to a “team player” and many NBA teams certainly use analytics beyond just assists to evaluate passing. Even still, one tool I’ve found to be valuable here at Hoopdata is the break-down of assists based on where they set up a shooter. That is, breaking assists down by scoring range can give us some more information about how someone is helping their teammates, where assists leading to threes and shots at the rim are probably of greater value than assists leading to mid-range shots.

So I wanted to look at some players who may benefit from changes in their point guard, or for a point guard, the players around him. The following analysis is subject to some bidirectional correlation, since a point guard’s assist totals are subject to the shooting efficiency of the players he’s passing to, while the shooting efficiency of players is subject to the quality of point guard play as well.

Regardless, I wanted to look specifically at point guards who assisted on a lot of three-point field goals and players who had a lot or few of their three-point field goals assisted on. This first table shows the leaders in assists per game leading to three-point field goals, and the percentage of their total assists that the number represents.

Here we see a lot of the usual suspects in terms of assists, but a few stick out as notable. For one, Turkoglu sets up a ton of three-pointers relative to his overall assist rate, as does Jameer Nelson. This obviously has something to do with Orlando’s three-heavy offense around Dwight Howard, as they were first in the league in three-point attempts. I’d suggest you’ll see both of these players take a serious step back in their assist numbers with the loss of Dwight, three-point field goal leader Ryan Anderson, and Stan Van Gundy’s relatively unique offensive system.

This second table shows the league’s leaders in terms of the percentage of their three-point field goals that were assisted on. Surprisingly, Steve Novak just missed the cut with 97.7%, though I expected him to be at 100% since all he does is spot up.

Here we see that, even with more help than just about anyone, Gordon Hayward still struggled a bit from deep. We also see that Ryan Anderson, the league’s three-point field goal leader, may have been a by-product of a three-friendly system, something he may not benefit from on a Hornets team with Greivis Vasquez and Austin Rivers at the helm. Additionally, we see that Jared Dudley may suffer from the loss of Steve Nash, but Antawn Jamison is moving to a nice situation where he’ll be a spot-up option for the Lakers with an insane Nash and Dwight pick-and-roll combo and another great passer in Pau Gasol. He may be past his prime, but I could shoot 40% on threes on that roster this year.

This third table shows the league’s leaders in total three-point field goals, as well as the proportion assisted on.

It’s interesting to see both Deron Williams and Joe Johnson on the list, especially since Deron led the league in assists leading to threes while Johnson had a large portion of his threes assisted. Pairing them together could make both even deadlier, lending credence to projections of Brooklyn as an offensive juggernaut (defense not included). We also see that Brandon Jennings is the king of calling his own numbers for threes, showing the highest proportion of unassisted threes among the leaders.

Once again we see a Magic impact, as J.J. Reddick could lose much of his value in the new-look offense in Orlando. We also see that James Harden had a fair proportion of his threes assisted on, though it’s not extreme either way – and while Jeremy Lin wasn’t among the leaders in helping on threes, he sure found a way to get Steve Novak involved. It’s been said a lot the past few days, but the most interesting part of Harden in Houston may be how he responds to increased focus from top-tier wing defenders.

These were just a few of the leaders, with somewhat random cut-offs and analysis. Are there any other players you could see having large gains in their three-point efficiency or volume due to roster changes?

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Stats And Box Scores Temporarily Down

by 30. October 2012 21:36

Due to the recent storm affecting me in Long Island, NY and Matt in Northern New Jersey, we're both unable to get consistent internet let alone electricity for the time being. We also have some unfinished maintenance to do on our parsing program once our electricity returns, so we could be without stats for a little while seeing how electric companies are putting estimates at 7-14 days for power to be returned at the moment. We're sorry for the inconvenience, and will work to get the site up and running the way everyone is used to as soon as we can, while also still providing content from our writing staff for the time being. 

 

Thanks.

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Does Preseason Matter?

by Blake Murphy 29. October 2012 07:34

Preseason doesn’t matter. Or say they say. And so Ray Allen says.

This axiom has been long held, and it makes some sense. Players on new teams are learning to play with each other, coaches are experimenting with schemes and line-up configurations, and stars are playing smaller minutes at lower effort levels to ensure a healthy start to the regular season.

At the same time, it feels like there is anecdotal evidence of signs from the preseason being strong indicators of performance changes in hindsight.

Looking at player stats, Kevin Pelton of Basketball Prospectus recently wrote a piece that deemed the preseason to be neither completely meaningless nor completely useful. Pelton summated his findings and his feelings as such: “It matters, but it's not nearly as meaningful as a player's track record. What the numbers indicate is that we ought to approach the preseason, like anything else, in Bayesian fashion. When the results are consistent with what we already know, they strengthen our conclusion.”

As a Toronto Raptors supporter, I’m more interested in present at what preseason results can tell us about team performance. My thought was that if I looked at it, I’d find largely the same result as Kevin did with players – there will be some correlation between preseason success and team success, but a lot of it will just strengthen our preconceived notions. That is, the strong preseason play of Chicago shows that they can be good even without Derrick Rose in the interim, while the poor play of Orlando confirms their status as cellar dwellers for this year.

With teams, there are more confounding factors in winning percentage than with player stats, as outlined above. But still, I wanted to see if the 6-1 record the Raptors posted this preseason is a sign of things to come or just a red herring in a small sample pre-season where the Raptors were the rare team playing all of their regulars a fair amount.

Method

I pulled pre-season data from 2005-06 to 2010-11 (I left out last year’s preseason since the lockout shortened it to two games per team), and compared it to regular season performance from 2004-05 to 2010-11. What I was looking for was to see if pre-season record correlated with regular season record. I also wanted to see if changes in performance level (that is, a team performing much stronger in the preseason than they had in the previous year’s regular season) correlated with changes in actual year to year winning percentage.

Results

Not surprisingly, the correlation between pre-season winning percentage and same-season regular season winning percentage wasn’t that strong, with a correlation of just 31.7% and an R2 of just 0.1. So yes, preseason numbers are correlated with regular season numbers, but the relationship is not strong. This data and this chart tell us little about what to expect from surprising preseason performances, since they can easily be chalked up to the randomness of a small sample size or the caveats outlined earlier such as player usage and team experimentation.

I also wanted to see, though, if just changes in performance could be signalled by improvements or setbacks in the preseason. I took the difference between a team’s preseason record and their regular season record in year n-1 and compared it to the change in their regular season records. My hope was to see if a big jump in the preseason signalled a coming improvement in regular season performance or vice versa for teams that would struggle. This time, there was a slightly higher correlation at 38.9% with an R2 of 0.15. This still isn’t strong, of course, but it at least shows that preseason changes aren’t entirely random.

So no, the preseason is not entirely irrelevant. If your team was unexpectedly good, you may have reason to be hopeful. But if your team was unexpectedly bad, there is plenty of room for you to reasonably ignore that fact (Lakers fans) since these relationships are anything but pronounced.

2012-13 Impact

For this year, the team’s with the biggest drop in performance from 2011-12 regular season winning percentage and 2012-13 preseason winning percentage were as follows. This doesn’t mean they’re doomed by any means, but there is reason for concern, or at least reason to go back and examine the preseason game tape or box scores to see if there were some obvious reasons. Reasons like Metta World Peace saying the Lakers’ 0-8 record is just the team showing love to their fans.

In terms of reasons for optimism, the Raptors and new additions Kyle Lowry and Jonas Valanciunas (among others) top the list after a 6-1 preseason. Despite the objections of DeMar DeRozan, even the most negative projections are showing some amount of improvement for the team (John Hollinger’s 33-win prediction would actually be a gain of four wins given last year’s prorated record). While they’re unlikely to be an .857 team, my prediction of 38-44 seems completely reasonable as only two of the 14 teams in this sample to have a preseason winning percentage of .857 or better finished below .500 that year.

Here we see that the Warriors, Kings, Sixers and T-Wolves also have some cause for cautious optimism. Of note is that of the top-20 teams in this sample in terms of preseason improvement over the previous year, only three failed to improve their actual regular season record from the season before.

So yes, feel free to get a little excited about a strong preseason. Don’t go overboard and bet the mortgage on Vegas over/unders, but safely bet your friends your team improves on last year’s record at least a bit. As for the laggards, well, there are plenty of counter-examples to this relationship, so take the advice of Metta and Ray and just cross your fingers.

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