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Posts Tagged ‘Dirk Nowitzki’

I’m a big fan of On/Off data, which compares a team’s point differential with a player on the court versus when he’s off the court. I’ve referenced it frequently in the past and think it’s one of the more telling reflections of a player’s value to his team in the advanced stat family.

The nice part about On/Off is that it represents what actually happened. The problem with On/Off is it ignores the reasons why it happened. And sometimes, it creates a fuzzy picture because of it.

For example, let’s suppose Kobe Bryant plays the first 40 minutes of the a game and injures his ankle with the score tied at 80. LA wins the game 98-90. The Lakers were dead even when he was in the game, and +8 with him out of the game – Bryant’s on/off would be -8.

In this case, sample size is an issue. But that becomes less of a problem over the course of an entire season. The real concern is the normal variance involved in everyone else’s game. Practically speaking, it takes little outside the norm for Kobe to have played 40 brilliant minutes while his teammates missed a few open shots, and for the opponent to miss a few open shots down the stretch while Kobe’s teammates start hitting them.

The tendency is to look at a result like that and conclude that Kobe hurt his teammates’ shooting and when he left the game it helped their shooting. He very well may have by not creating good looks for them.

Then again, players hit unguarded 3-pointers about 38% of the time. Which means if the average shooter attempts five open 3-pointers, he will miss all five about 10% of the time, simply based on the probabilistic nature of shooting. A fact that has little to do with Kobe or any of the other players on the court.

In our hypothetical situation, all it takes is an 0-5 stretch from the opponent and a 3-5 stretch from LA to produce Kobe’s ugly -8 differential. The great college basketball statistician Ken Pomeroy ran some illuminating experiments on the natural variance in such numbers. His treatise is worth the read, but the gist of it is that his average player — by definition — produced a -57 on/off after 28 games (-5.7 per game) due to standard variance in a basketball game outside of that player’s control. Think about that.

For fun, I just ran the same simulation and my average player posted a +5.6 rating of his college season:

Average Player Simulation

So in two simulations, the average player’s On/Off ranged from -5.7 to +5.6. One guy looks like an All-Star, the other like an NBDL player.

“The Team Fell Apart When Player X Was Injured”

This is a common argument for MVP candidates: Look at how the team fared when he missed a few games and conclude the difference is the actual value a player provides to his team. Only this line of thinking runs into the same problems we saw above with on/off data.

Let’s take Dirk Nowitzki and this year’s Dallas Mavericks. In 62 games with Dirk, Dallas has a +4.9 differential (7.8 standard deviation). In nine games without Dirk, a -5.9 differential (7.5 standard deviation).

Which means, with a basic calculation, we can say with 95% confidence that without Nowitzki, Dallas is somewhere between a -1.0 and -10.8 differential team. Not exactly definitive, but in all likelihood they are much worse without Dirk. OK…but we can’t definitively say how much worse they are.

In a small sample, we just can’t be extremely conclusive. In this case, nine games doesn’t tell us a whole lot. New Orleans started the season 8-0…they aren’t an 82-win team.

We can perform the same thought-experiment with Dirk’s nine games that we did with Kobe’s eight minutes to display how unstable these results are. Let’s say Dallas makes three more open 3’s against Cleveland and the Cavs miss three open 3’s. What would happen to the differential numbers?

  1. That alone would lower the point differential two points per game.
  2. Our 95% confidence interval now becomes -12.1 points to +4.4 points.

That’s from adjusting just six open shots in a nine game sample.

Jason Terry — a player who benefits from playing with Dirk Nowitzki historically — had games of 3-16, 3-15 and 3-14 shooting without Dirk. He shot 39% from the floor in the nine games. By all possible accounts, Terry is better than a 39% shooter without Nowitzki. He shot 26% from 3 in those games. Let’s use his Atlanta averages instead, from when he was younger and probably not as skilled as a shooter: How would that change the way Dallas looks sans-Dirk?

Well, suddenly Terry alone provides an extra 1.7 points per game with his (still) subpar shooting. The team differential is down to -2.2 with a 95% confidence interval of -10.4 to +6.1. Just by gingerly tweaking a variable or two, the picture grows hazier and hazier.

Making Sense of it All

So, what can we say using On/Off data? It’s likely Dallas is a good deal better with Dirk Nowitzki. But, hopefully, we knew that already.

To definitely point to a small sample and say, “well this is how Dallas actually played without Dirk, so that’s his value for this year” ignores normally fluctuating variables — like Jason Terry or an open Cleveland shooter — that have little to do with Dirk Nowitzki’s value. So while such data reinforces how valuable Dirk is, we can’t say that’s how valuable he is.

We can’t ignore randomness and basic variance as part of the story.

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True Shooting percentage is a popular statistic roughly designed to capture points per shot. But since it mashes together 2-point field goals, 3-point field goals and free throws, the final percentage isn’t exactly intuitive. What does it mean to have a TS% of 55% versus one of 60%? Precisely, how much more efficient is that?

Let’s look at three different types of players: low-usage, medium-usage and high-usage, defined as

  • low-usage players take roughly 10 attempts per 75 possessions (FGA’s + FTA’s*0.44)
  • medium-usage players take roughly 15 attempts per 75 possessions
  • high-usage players take roughly 20 attempts per 75 possessions

Current examples: Shane Battier is low-usage, averaging 9.4 attempts per 75, Kevin Garnett is a medium-usage player, averaging 16.2 attempts per 75 and Dirk Nowitzki is high-usage, averaging 21.3 attempts per 75. Kobe Bryant is the league-leader right now, at just over 27 attempts per 75 possessions.

So, what is the relationship between TS% at these rates and actual scoring efficiency? Well, the more a player shoots the more the percentage points matter. By definition, there is a simple linear relationship between TS% and points, shown below graphically:

So for someone like Battier, every one percent change is worth about 0.2 points. For Garnett, about 0.3 points and for a high-usage guy like Nowitzki, every single percent change is worth about 0.4 points. So, returning to the idea of low, medium and high-usage players, we can look at their affect on a team’s Offensive Rating. For every one percent change in TS:

  • low-usage players change an ORtg by 0.2 points
  • medium-usage players change an ORtg by 0.3 points
  • high-usage players change an ORtg by 0.4 points

That means when comparing high-usage stars, a small change in TS%, say 2%, roughly equates to almost 1.0 point in offensive efficiency. This is not inconsequential, as that approximates to an SRS point, usually good for a handful wins in a season. A 4% change is worth about 1.5 points in ORtg, and a 6% difference 2.5 points or nearly 3 SRS points. A change of that magnitude in SRS is often the difference between an average team and a solid playoff team, or a solid playoff team and a title contender.

In other words, the 5.9 % TS difference between LeBron James in 2010 (24.8 “attempts” per 75) and Kobe Bryant in 2010 (24.7 “attempts” per 75) is worth about 2.9 points, based on their shooting efficiency.

Keep that in mind when comparing TS% numbers. For a better look at estimating overall “offensive efficiency” as it changes with usage see this post at Basketball-Reference.

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Despite his prolonged success with so many different teammates, Steve Nash is still bombarded with criticisms of being some sort of “system” player. Some go as far as asserting that Nash’s teams are inherently flawed because of their offensive slant, and as a result they never win.

My hunch is, as is the case so often in sports analysis, that people are misattributing the concept “winners” vs “losers” and “winning systems” vs “losing systems.” Karl Malone is the ultimate example of this in the NBA.

Malone was, at times, dominant in his Western Conference playoff runs at the end of the 90s. How can someone be a “loser” or in a losing system if he continues to be the primary driver of winning teams, in both the regular season and the playoffs? Yes, people make a big deal about his statistical decline in the postseason, but Malone also had his fair share of excellent performances at big times. But because he lost to Chicago…it means he “couldn’t get over the hump.” He’s a “loser.”

As if asking John Wooden’s early 70s UCLA teams to play the NBA champion after winning the NCAA title game would somehow make them a loser.

“That Wooden,” they’d say, “his system doesn’t work…can’t win the big one.”
Peyton Manning was hamstrung with this ridiculous logic, in football, of all sports (21 other players with extremely complex, non-quantified interactions). Like Malone, did his performance decline at times in the postseason? Absolutely. Like Malone, was he probably wired slightly differently than Joe Cool or Michael Jordan? Armchair psychology says yes.

But sometimes there’s just a better team in the way.

And in Manning’s case, he was suddenly branded a “winner” after having arguably his worst overall postseason in 2006. He got “over the hump” because offensive linemen fell on fumbles at the right time, Reggie Wayne fumbled the ball into the air to himself, Troy Brown ran a wrong route, Jabbar Gaffney dropped a pass, Ellis Hobbs was flagged for a phantom pass interference penalty the NFL later apologized for and half the Patriots defense cramped up in the second half after flying across the country twice in a week. What do any of those events have to do with whether Peyton Manning inherently is a winner or loser, whether he plays in a winner or losing “system?”

Nothing.

So like Nash, unless we think that his mere presence on the court demands a style to be run through him which literally causes his team’s defense to struggle, I don’t understand how

(a) running into better teams (eg Duncan’s Spurs) or
(b) never being given adequate defensive pieces

is an indictment of Steve Nash’s offense.

Yes, the offensive/defensive rating stats are not perfect representations of what they attempt to represent (they are darn good though). And besides looking at Nash being on and “running’ the best offenses in NBA history (both in Dallas and Phoenix), we can also simply watch a basketball game and see whether such an assertion is plausible.

Maybe Nash’s great offenses are because he cherry picks and puts his team at a defensive disadvantage?

Maybe Nash’s great offenses are because he inherently requires offensive players who aren’t good at defense?

I’ve seen a lot of basketball — too much, according to many — and I see absolutely no indication of any of these negatives when I watch Steve Nash play. To address the big points often levied against him:

Nash suddenly (ie inexplicably) became a superstar when he went to Phoenix

Yes, Nash was helped by the rule changes that freed perimeter players. But you know what, so was Wade, Kobe, Pierce, Iverson, etc. You know what else helps Nash? The 3-point line. Rules are rules. But the notion that he went from nothing to something overnight is simply wrong.

Look at his shooting percentages from 97-99. He was a late bloomer. A learner. Constantly improving his shot and understanding of the game while attempting to find a rhythm as a small-college reserve. Anyone who has struggled through a lineup knows this can have a big impact on a young player. Yet in his second year he was a fantastic backup PG.

In 2000 his shooting clearly improves. In 2001 he is the full-time starter. In 2002 he is an all-nba player at 27…which happens to be his third year starting. 2003, all-nba again. They run more of the offense through Nash in 2004, but no one realizes the subtle role change and they only see diminished ppg and fewer wins (due to lack of defense). Never mind it was the best offense, by relative ORtg, in NBA history, despite Dallas only shooting 34.8% from 3.

By then he’s 29, Cuban makes a miscalculation about his age, despite so few miles on the odometer. He’s “old” and coming off a “down year.” Dallas has a PG in the wings in Harris and needs to focus on defense, so they don’t resign Nash. The Suns make him the center-piece, they run pick and roll to death, the league changes perimeter rules, and logically Nash’s impact jumps.

Yet everyone concludes it was the system. A miracle. An unjust MVP. He is NOT the first player in NBA history to take a late arc by age. It’s not like he was a Canadian kid from Santa Clara backing up Kevin Johnson and Jason Kidd in his first two seasons. Oh wait, he was…and still impressed off the bench.

Why did the Mavericks reach the Finals after he left?

In 2004 Nash’s teammates were terrible defensively. Defense is critical in playoff settings. Antoine Walker, Antawn Jamison and no center aren’t exactly a recipe for good defense…how is that team supposed to win? Conversely, in 2006, simply plugging in a defensive part at center — Diop or Dampier — as well as defensive upgrades like Adrian Griffin, completely changed the tenor of the Mav’s playoffs chances. (I collected a nice sum of money in 2006 bc of it — nice foul Manu Ginobili!)

What does any of that have to do with Steve Nash’s offense…or his offense’s affect on defense?

Why didn’t Nash win a title in Phoenix?

In Phoenix, the Suns came together in 2005 and with an interior combination of Amare Stoudemire and Shawn Marion were absolutely no match for San Antonio with Tim Duncan and Nazr Mohammed roaming the paint. (They were, however, so offensively potent they had no problem running through Dirk’s Mavericks to the WCF.) Nash didn’t exactly disappoint in the series, either. Was Nash’s offense at fault for Duncan and Ginobili toying with the Suns defense?
In 2006 they were saddled with injuries…Nash again led them to the WCF with a bunch of small forwards…where they encountered the aforementioned and improved version of the Mavericks.

In 2007, they were, to me, the best team in the NBA. The defensive efforts were good enough to win (13th in DRtg). They sure looked like the better team in the San Antonio series, considering his G1 injury kept him out down the stretch due to bleeding, the controversial suspensions and officiating in G3 and G4, respectively and playing G5 with six players: Nash and Bell, Marion, Thomas, Barbosa, James Jones. They lost by 3 points to a fully loaded dynastic Spurs team. In G6 they were exhausted, clearly. Ginobili, again, crucified them in those 2 final games. Did he do so because of Nash?

Nash’s Pace/System is only successful at the expense of good defense

Finally, just watching the game, Nash doesn’t need one-dimensional offensive players or weak defenders to cheat and leak out on the break (Nelly-ball?), he is arguably at his best in the halfcourt and in the pick and roll. It’s probably the biggest single reason why Phoenix’s offensive numbers don’t plummet in the playoffs when the pace is slowed. If anything, that’s a boost for Nash’s value, is it not?

Time and time again, Nash’s play seemingly wills Phoenix to big wins. In 2005 v Dallas, in 2006 v LA, even just last year in the playoffs. That flawed “system” of his again had Phoenix neck and neck with a giant Laker team. His ridiculous 4th quarter against San Antonio with his eye swollen shut.

I don’t know how to view any of that as something inherently flawed. As a losing system or a losing player. And I do believe, with extreme conviction, that if Phoenix gets by San Antonio in 07 or LA last year, Nash would be viewed differently…because of factors that have nothing to do with Steve Nash.

Give him a defensive-molded center and another capable defender, a shooter or three (a dime a dozen, see: Jones, James) to go along with a No. 2-type player and that’s an NBA-championship level team every single year. Kind of like Phoenix in 2007. (And they had 34-year old Kurt Thomas playing that big-man role.)

Four or five years ago I was not sold on Nash. But I find it impossible to watch him or analyze him/his teams and think that he’s anything other than one of the best offensive players in NBA history. He’s certainly one of the best shooters and passers in NBA history, and he uses those weapons to run an unstoppable barrage of pick and roll sets.

And if mimicking his “system” were presumably so easy…why hasn’t anyone else done it?

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