Playoffs Pessimism and the Plexiglass Principle

October 5th, 2015 | by Matt Pacenza
Photo by Bart Young/NBAE via Getty Images

Photo by Bart Young/NBAE via Getty Images

Last year’s Jazz team improved by 13 games, from 25 wins to 38.

Given that the Jazz’ core players are young and improving, most fans are projecting a significantly better record for the coming season — enough to land the team a playoff spot.

Making the playoffs likely takes at least seven more wins, given that the 8th seed has won 45 to 49 games in the Western Conference the past five years.

I’d love to see playoff games in May. But I think there’s a strong chance we won’t. Let me put on my Eeyore hat for a moment, and explain why I think those seven extra wins in 2015-16 might be tougher than most Jazz fans think.

Fact: Most teams that improve significantly from one year to the next don’t then continue improving significantly. That principle is well known in baseball analytical circles and is known as the “Plexiglass Principle.”

Should we expect it to apply to the Jazz? Let’s dig deeper.

The Principle

Baseball writer (and now Red Sox consultant) Bill James might not be the inventor of sports analytics, but he’s certainly the figure who did the most to spread its gospel. If you haven’t read his writing and insights, run out and do so.

James came up with all kinds of theories about player and team value, starting in the late 1970s. Many still hold true today. One is the Plexiglass Principle. Grantland’s baseball writer Jonah Keri explained it succinctly in this 2012 column:

A team that improves in one season tends to decline the next, and vice versa. It was an easy idea to understand, but a tough one to believe. We human beings are hard-wired to hate randomness. So we look for patterns in everything. Thus a team that wins 75 games one year and 81 the next is perceived to be on the rise, destined for greater things. A team that slips from one season to the next is on its way down, headed for a stretch of lean years. Fans make this mistake, writers and prognosticators make this mistake … even MLB general managers make this mistake.

A simple concept, but does it apply to the modern NBA? I decided to run some numbers.

The Data

I looked at the last 10 seasons, starting in 2004-05, and generated a list of teams which improved by more than 10 games, one season to the next. I then looked at what those teams did in the following year.

More teams had significant improvements in the past decade than I had guessed (Which explains why I chose to only look at the past 10 years — this took time!) One quick note: 2011-12 was of course a lockout season. In order for this exercise to work, I pretended each team had played 82 games, extrapolating from their 66-game season winning percentage.

OK, now the results (I’ll paste the full table at the end of the article for the curious):

  • In the past decade, 38 NBA teams have had a season in which they won at least 10 more games than the year before.
  • In the following season, 19 of those teams had a worse record. 18 had a better record. And one had the same record.
  • On average, the 38 “big jump” teams saw their record decline by one game the following year.

So, you might think, that’s not bad. If roughly half the improving teams continued to get better, then that gives the Jazz pretty good odds. I’ll admit I expected James’ theory to hold up a big more strongly, but remember for the Jazz to make the playoffs this year, they’ll likely need at least seven more wins.

So how many of the Jazz’ fellow “big jump” teams managed seven more wins in the third year?



Just five of 38 “big jump” teams saw their record continue to improve, by at least seven games, in the third year.

The Discussion

Let’s take a look at each of those teams briefly — and see if we find teams like the 2015-16 Jazz. When we think of “big jump” teams which keep improving, four types come to mind. First, a team that drafts a game-changing star. Think LeBron or Durant or Anthony Davis. Second, a team that acquires a star (or two) via trade or free agency. Think, Cleveland re-acquiring LeBron. Or the Clippers getting Chris Paul.

Third, think of a young team with multiple players maturing and improving. This, clearly, is the path the Jazz are taking. Fourth, a team that benefits from a new coach. Again, the Jazz fit in this category.

Of course, a team could benefit from a combination of these factors.

Which kind of “big jump” teams have tended to have sustained improvement?

Charlotte 2011-14 (9 wins to 21 wins to 43 wins)

The 2011-12 Bobcats had the worst winning percentage of any team in NBA history. And the next year they were ordinarily dreadful, but not historically so. What changed? Well, Mike Dunlap replaced Paul Silas as coach. And a couple young players got decent, primarily Kemba Walker and Gerald Henderson. Rookie Michael Kidd-Gilchrist joined the team and free agent Ramon Sessions added above average offense. Just enough maturation and fresh blood to become — a bad team!

But in that third year, the Bobcats really improved — and grabbed a playoff spot. Again, a new coach: Steve Clifford, widely credited with boosting the team’s defense. A big free agent signing — Big Al Jefferson put up a 22.7 PER — plus the team signed FA Josh McRoberts, who actually led the team in VORP. Their young players, largely, didn’t show big improvement on offense, but Big Al, McRoberts and the stronger defense was credited for most of their sustained increase.

The Jazz can take some inspiration from the Bobcats (now that’s a sentence one doesn’t type much) in their coaching upgrade and defensive commitment, but haven’t added free agents this offseason likely to add nearly as much as Big Al or even McRoberts.

Utah 2004-07 (26 wins to 41 wins to 51 wins)

Ha! The 2005-6 Jazz added two key players: Free agent Mehmet Okur and rookie point guard Deron Williams. And they kept improving the third year, thanks to Deron’s continued improvement, plus the addition of two productive rookies — Paul Millsap and Ronnie Brewer.

The Jazz of nine years ago should offer inspiration. It may be unlikely that any of this Jazz team’s new additions will offer as much as Millsap did (as a rookie, he had a PER of 17 in 18 minutes per game.) But that squad, and this one, are built around a core of young, improving talent. On the 06-07 Jazz, Williams was just 22, Boozer 25 and even Okur only 27.

Portland 2005-08 (21 wins to 32 wins to 41 wins)

The Trail Blazers of 2005-06 had bunch of young players, but only 24-year-old Zach Randolph was particularly productive. The team then hit a home run in the draft, adding not just Brandon Roy but LaMarcus Aldridge, both of whom were immediately useful. Sophomore Jarrett Jack also improved, as did Randolph.

And in that third season, when the Blazers hit .500, they again benefited from the continued growth of a young core, particularly Aldridge and Roy.

This team strikes me as the best model so far for the Jazz. The Blazers drafted well and improved steadily around young talent.

LA Lakers 2006-09 (42 wins to 57 wins to 65 wins)

In 2006-07, the Lakers made the playoffs thanks to a terrific Kobe season, plus help from rookie Andrew Bynum and a solid Lamar Odom year. But that next year, the Lakers really took off, thanks in large party to their trades for Pau Gasol and Trevor Ariza. That team, of course, lost in the NBA finals to the Celtics.

But they continued to improve, despite not adding any significant new talent in 08-09. Bynum stayed healthier (but still missed 30 games) and the core of Bryant, Gasol, Ariza, Odom, Fisher and Bynum brought the team an NBA title.

It’s not clear how much the Jazz can take from that Lakers run. LA was a more mature team, with brighter stars, but like the Jazz their core stayed together and kept getting better.

Orlando 2006-09 (40 wins to 52 wins to 59 wins)

Second year star Dwight Howard led the Magic to 40 wins and a playoff berth in 2006-07, before the team took a big leap forward thanks in part to a new coach (Stan Van Gundy) a free agent signing (Rashard Lewis) and improved years from Howard, Jameer Nelson and Hedo Turkoglu.

That jump continued in 2008-09, landing the Magic in the NBA finals. A few young players contributed more (rookie Courtney Lee was solid) but the biggest factor was Howard’s arrival as an legitimate MVP candidate. He was the defensive player of the year and had a PER over 25. That, plus a decent supporting cast, was enough for seven more wins and the third best record in the East.

The Magic’s run of improvement feels a bit different than the Jazz, given the lack of a star comparable to Howard.

The Conclusion

As we can see, teams that have gotten better and then kept getting better are the exception. But Jazz fans can and should draw some solace from the few that did it. Many, if not all, of them built a path of ongoing improvement strong coaching and the growth of young talent — just like Utah.

However, as we noted earlier, the odds aren’t exactly in the Jazz favor. Winning seven more games this year, on top of the 13 added wins last year, is a feat few teams have mastered.

There is something different about this Jazz team, though. Maybe they weren’t “really” a 38 win team last year. Maybe they were actually closer to the 19-10 team that ended the year. And so, maybe, we’re not actually looking for the Jazz to continue to significantly improve, but rather to consolidate improvement they really accomplished last year.

That question — are late season runs more predictive than a full season record? — belongs to another post.

Part 2 on Playoff Pessimism to come.

And here’s that full table of the last decade’s “big jump” teams:

Team Period Y1 Y2 Y3
LA Clippers 2004-06 37 47 40
LA Lakers 2004-06 34 45 42
Milwaukee 2004-06 30 40 28
New Orleans 2004-06 18 38 39
Detroit 2004-07 54 64 53
Utah 2004-07 26 41 51
Houston 2005-07 34 52 55
New York 2005-08 23 33 23
Portland 2005-08 21 32 41
Toronto 2005-08 27 47 41
Boston 2006-09 24 66 62
LA Lakers 2006-09 42 57 65
New Orleans 2006-09 39 56 49
Orlando 2006-09 40 52 59
Cleveland 2007-10 45 66 61
Miami 2007-10 15 43 47
Portland 2007-10 41 54 50
Memphis 2008-11 24 40 46
Milwaukee 2008-11 34 46 35
Oklahoma City 2008-11 23 50 55
Brooklyn 2009-12 12 24 27
Chicago 2009-12 41 62 62
Golden State 2009-12 26 36 29
Miami 2009-12 47 58 57
New York 2009-12 29 42 45
Philadelphia 2009-12 27 41 43
San Antonio 2009-12 50 61 62
LA Clippers 2010-13 32 50 56
Minnesota 2010-13 17 32 31
Brooklyn 2011-14 27 49 44
Charlotte 2011-14 9 21 43
Denver 2011-14 47 57 36
Golden State 2011-14 29 47 51
Charlotte 2012-15 21 43 33
Phoenix 2012-15 25 48 39
Portland 2012-15 33 54 51
Toronto 2012-15 34 48 49
Washington 2012-15 29 44 46
Matt Pacenza

Matt Pacenza

When he isn't writing about the Jazz, Matt Pacenza is an environmental activist, Arsenal fan and world-class blowhard about many matters. A native of upstate New York, with a background in journalism and nonprofits, Matt lives near Liberty Park with his wife and two sons.
Matt Pacenza


  1. IDJazzman says:

    I know it’s is difficult to have definitive predictions when so many variables are at play, but I think to read the data properly, apples must be compared to apples. As you pointed out, the Jazz are a young team with a young coaching staff, which can bode well for future improvement. Teams that improve because of trades and acquiring more experienced coaching will hit their peak much quicker. It might take a few more years before we really know what the potential of this young Jazz team is. You make a good point about stars making a big difference, especially with the immediate improve of some teams. Here again, do the Jazz have a true star in Rudy Gobert? Is Rudy close to his max potential? I think we are starting to see the plateauing of Hayward and Favors, for this team to improve, others have got to be able to take them to another level. Rudy might can, as it kind of showed that he did at the end of last season. Maybe Exum and Rudy are the Jazz’s future elite players, If not, then maybe the Jazz’s potential is about 45 wins and they start to plateau. Hope springs eternal and I am hoping the Jazz have enough talent and potential stars in Rudy and Exum that they can help take this team to near 60 wins in 2 or 3 years.
    For this year, I think the end of season 19-10 record is a good indication that this team is headed for the 8th seed this year and they will make another jump.

  2. Brent says:

    The NBA is the most difficult professional sports League to improve in. It is also the most predictable league as well. Baseball is much more random. Hence, I don’t think the Plexiglass analogy is a good one.
    In the NBA teams generally rise or decline. Large changes are usually only brought on by massive free agency signings or exodus’. Otherwise young teams continue to grow get better. Old teams begin to decline and get worse.
    Don’t discount a team because it made a 13 game improvement. Granted that was large but it was largely brought on by a coaching change and management’s decision to finally play their best players. In other words, the ’13-’14 team was held back (tanked) by Corbin and the GSW trade that saw us start Richard Jefferson at the 3 and Marvin Williams at the 4. Those spots are clearly best occupied by our best 2 players (Hayward and Favors).

  3. Greg Hayes says:

    I think it should only be fair to mention though the reasons why the jazz made improvement and when exactly they did make that improvement. Why? Defense! Pure and simple is defense. Our offense wasn’t the greatest but that is also because they need more cohesion together in order to form a better offensive unit. Why did we get better on defense? Rudy Gobert! Yes the whole team together did play pretty good defense and Millsap and Exum are great defenders. But, Rudy Gobert is a game changer. However, he did not see his first start in a Jazz uniform until after the All-Star break. By this time we already had a man named Enes Kanter who was one of the worst defenders the Jazz had on their team since Carlos Boozer, maybe worse! Not to mention his all me attitude didn’t sit too well with the players. The other reason to mention their improvement is the when because it ties exactly into why. The Jazz had a 19-10 record after the all-star break, when Rudy Gobert was entered into the starting lineup and their defense went from one of the worst in the league to one of the best in the league. Now, how many of those teams that did not make a second big improvement had a defensive anchor to the likes of Rudy Gobert. That’s easy to answer! None! The reason why is Rudy Gobert is a type of defender that does not come by very often. If we are to look at the Jazz from last season and project how they will do the rest of the season I don’t think we can look at the season as just one whole season. We have to look at last season as two distinctly different seasons. The Kanter Era and the Post Kanter era. The evidence for the impact that trade had on this team is too obvious it is hard to ignore. If we take the Jazz winning percentage for after the all-star break this team is a 53-54 win team. Now, I am not saying that they will necessarily win that many games this year but if they did I would not be surprised. The reason why is that a defensive minded team and one of the best in the league does not simply change or get worse after one season. The same team that ended the season was basically kept in tact and these young players have now had a season to get better, not to mention the return of Alec Burks. If this team was simply a middle of the field defensive team I would think differently. But, they’re not!!! This team will be one of the top 5 defensive teams in the league this year no doubt, maybe even top 3. Look at history and the amount of teams that make the playoffs when they play that type of defense. It’s almost 99% of the time. If anything I think history will show that the Jazz making the playoffs this year is more likely than not.

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