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Does the NBA preseason matter?

by Roland Beech, 82games.com

(revised to include 2007-08 season data)

Sure the preseason games matter to the players trying to make the team, the veterans trying to test out their bodies coming from injuries, and for the league itself perhaps to have some build up for the regular season tipoff. The question though is do the preseason records matter?

Is a team's won-lost mark in the exhibition games any indication or tip-off as to how the regular season will unfold? You hear announcers hand down their opinions, but I've yet to see any study on the matter...so let's examine the issue 82games style!

Tracking down preseason stats is no easy feat, but I've compiled a five year database for the 2001-02 season through 2007-08. That's not a huge sample, but a decent look for our purposes.

Correlations:
.35 Preseason win% --> Regular Season win%
.55 Last Year win% --> This year Regular Season win%
.31 Change in this preseason win% vs last preseason win% --> Change in this year wins vs last year wins

Now the confidence intervals on these are large due to an n=206, but still it's fair to say that a .35 correlation is reasonably healthy and suggests that yes the preseason records do have some significance in setting a tone for how things may go when the real games begin. The NBA does have more consistency from year to year than many sports, the NFL correlation from one year's record to the next for example was just .25 in one recent five year span.

Also, the fact that an improvement in preseason win % from one year to the next has a .31 correlation to a change in regular season wins is also notable.

BEST preseason records ('01-02 to '07-08)
Year  Team Preseason Regular Season
2002-03  Detroit 8-0 1.000 50-32 0.610
2004-05  Phoenix 7-1 0.875 62-20 0.756
2005-06  Denver 7-1 0.875 44-38 0.537
2003-04  Utah 7-1 0.875 42-40 0.512
2007-08  Atlanta 7-1 0.875 37-45 0.451
2003-04  Memphis 6-1 0.857 50-32 0.610
2004-05  Denver 6-1 0.857 49-33 0.598
2002-03  New Jersey 6-1 0.857 49-33 0.598
2006-07  Toronto 6-1 0.857 47-35 0.573
2007-08  Orlando 5-1 0.833 52-30 0.634
2001-02  Minnesota 5-1 0.833 50-32 0.610
2001-02  Toronto 5-1 0.833 42-40 0.512
2006-07  Golden State 5-1 0.833 42-40 0.512
2005-06  Dallas 6-2 0.750 60-22 0.732
2002-03  Sacramento 6-2 0.750 59-23 0.720
2005-06  Phoenix 6-2 0.750 54-28 0.659
2006-07  Chicago 6-2 0.750 49-33 0.598
2005-06  Memphis 6-2 0.750 49-33 0.598
2005-06  LA Clippers 6-2 0.750 47-35 0.573
2004-05  Memphis 6-2 0.750 45-37 0.549
2005-06  LA Lakers 6-2 0.750 45-37 0.549
2004-05  Philadelphia 6-2 0.750 43-39 0.524
2004-05  Cleveland 6-2 0.750 42-40 0.512
2007-08  Toronto 3-1 0.750 41-41 0.500
2006-07  Orlando 6-2 0.750 40-42 0.488
2003-04  Seattle 6-2 0.750 37-45 0.451
2007-08  Indiana 6-2 0.750 36-46 0.439
2005-06  Houston 6-2 0.750 34-48 0.415
Average   46-36 0.561
Average gain of 4 wins from coming season compared to last


WORST preseason records
Year  Team Preseason Regular Season
2004-05  Seattle 2-6 0.250 52-30 0.634
2004-05  Sacramento 2-6 0.250 50-32 0.610
2002-03  NO/Oklahoma City 2-6 0.250 47-35 0.573
2004-05  Boston 2-6 0.250 45-37 0.549
2003-04  New York 2-6 0.250 39-43 0.476
2001-02  Washington 2-6 0.250 37-45 0.451
2006-07  Charlotte 2-6 0.250 33-49 0.402
2003-04  Philadelphia 2-6 0.250 33-49 0.402
2006-07  Portland 2-6 0.250 32-50 0.390
2007-08  Charlotte 2-6 0.250 32-50 0.390
2003-04  Phoenix 2-6 0.250 29-53 0.354
2002-03  LA Clippers 2-6 0.250 27-55 0.329
2001-02  Denver 2-6 0.250 27-55 0.329
2003-04  Washington 2-6 0.250 25-57 0.305
2005-06  Portland 2-6 0.250 21-61 0.256
2007-08  Seattle 2-6 0.250 20-62 0.244
2005-06  San Antonio 2-7 0.222 63-19 0.768
2001-02  Cleveland 1-5 0.167 29-53 0.354
2006-07  Cleveland 1-6 0.143 50-32 0.610
2007-08  Cleveland 1-6 0.143 45-37 0.549
2001-02  Philadelphia 1-6 0.143 43-39 0.524
2004-05  Atlanta 1-6 0.143 13-69 0.159
2003-04  Orlando 1-7 0.125 21-61 0.256
2002-03  Denver 1-7 0.125 17-65 0.207
2007-08  Miami 0-7 0.000 15-67 0.183
Average   34-48 0.415
Average decline of 4.6 wins from coming season compared to last

So that's some pretty nice visual confirmation for preseason believers. Of course it might cross your mind that preseason records could vary in significance based on the prior year success of a team. After all a great team the previous year probably lets the mainstay guys ease through the exhibition games with minimal minutes while the team looking to improve might be running the regular season starters out there for big minutes.

Correlation of Preseason Record to Regular Season Record:
.59 Teams coming off a less than 30 win season
.40 Teams coming off a 30 to 39 win season
.46 Teams coming off a 40 to 49 win season
-.02 Teams coming off a 50+ win season

Aha! You say. That proves it then, great teams can ignore the preseason. Well, not entirely, since the sample sizes again get too small to really have conclusive value. Still it is suggestive of that theory, and more importantly perhaps it seems that for a poor prior year team, the preseason results really do have some bearing on whether improvement can be expected.

Teams with winning preseason records off a <30 win season
Year  Team Preseason Regular Season Prior Yr
2004-05  Phoenix 7-1 0.875 62-20 0.756 29-53
2003-04  Memphis 6-1 0.857 50-32 0.610 28-54
2006-07  Toronto 6-1 0.857 47-35 0.573 27-55
2003-04  Miami 5-2 0.714 42-40 0.512 25-57
2006-07  New York 4-2 0.667 33-49 0.402 23-59
2003-04  Toronto 4-2 0.667 33-49 0.402 24-58
2007-08  Memphis 4-2 0.667 22-60 0.268 22-60
2003-04  Denver 5-3 0.625 43-39 0.524 17-65
2006-07  Atlanta 5-3 0.625 30-52 0.366 26-56
2007-08  Boston 4-3 0.571 66-16 0.805 24-58
2002-03  Houston 4-3 0.571 43-39 0.524 28-54
2004-05  Orlando 4-3 0.571 36-46 0.439 21-61
2003-04  Cleveland 4-3 0.571 35-47 0.427 17-65

To put it in perspective, the rare poor prior year team that strings together some wins in the preseason has seen an average gain of 17 wins in the next year!

Now if you extend it to look at any team <50 wins the prior year with a say .700 or better preseason it's a average gain of 7.5 wins.

All right, so which '07-08 teams have shown signs of life in '08-09 "meaningless" games?

6-2 Minnesota (22-60 last yr)

Are we destined to see some revival for the Timberwolves this coming season? Trying to project performance from the preseason alone is likely a foolish endeavor, but on the other hand if you're a fan of a team that's anything less than a rock solid 50+ win type, you might want to root for some exhibition wins after all.

One last oddity to wrap it up: teams that have improved their preseason win% over last year by .400 or more gain an average of 17 wins...this season that again tabs the Timberwolves, but also the Hornets who were .500 in '07-08 preseason but a perfect 1.000 this time out!

On the flip side, teams that lose .250 or more off their preseason win% have lost an average of almost six wins...this season Charlotte, Milwaukee, Sacramento, Memphis, Indiana, Toronto and Atlanta "could have done better" in the October classics.


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