Statitudes Statitudes

Luck of the Irish

How Celtics' fortune may keep Jordan out of playoffs

Posted: Tuesday March 25, 2003 3:11 AM
Updated: Tuesday March 25, 2003 3:13 AM

By John Hollinger,

Sometimes it's better to be lucky than good.

Take Boston, for example. Since the goal of the game is to score more points than the other team, you would expect a team that has been outscored on the season to be under .500, not well above it. But the Celtics have given up 54 more points than they've allowed this year, yet managed to stay comfortably above .500 at 38-33.

But how can I say they've been lucky, rather than just doing the right things at the right times to win games? Two reasons. First and most obvious, there's the fact that that's how it works out most of the time: The teams that win by the most are the teams that outscore their opponents by the most. Dallas, for example, has scored 610 points more than its opponents -- easily the best total in the league -- so it's not surprising that it also sports the best record at 53-17.

Second -- and this is the part that needs some explaining -- is the fact that teams like this year's Celtics, who win more games than you'd expect by looking at their points scored and points allowed, rarely give an encore performance the next year.

How do I know this? Because of something I call Expected Wins. Expected Wins is a tool I developed to measure how many games a team could be expected to win, given its point differential. The formula is remarkably simple (at least compared to some of the other stuff I've floated here): Take the team's average point differential, multiply by 2.7 and then add half the team's games played.

The Boston Celtics, for example, have a point differential of -0.7 and have played 71 games, so their Expected Wins is 34, which is one way of saying they should be 34-37 right now and not 38-33. Incidentally, that four-game differential is the biggest in the league this year -- all but three teams are within three games of their Expected Wins.

Getting the bounces
NBA's best and worst, wins vs. Expected Wins
BEST  Wins  Exp. W  Diff.  WORST  Wins  Exp. W  Diff. 
Boston  38  34  +4  New Jersey  42  47  -5 
Minnesota  45  41  +4  Memphis  29  26  -3 
Portland  44  41  +3  Miami  25  22  -3 
San Antonio  48  45  +3  L.A. Clippers  24  22  -2 
Atlanta  29  26  +3  Houston  37  39  -2 
But let's get back to the topic at hand. How do I know the Celtics have been lucky, rather than simply getting their points when it counts and not worrying about a few 40-point blowouts?

The answer lies in how teams fare in Expected Wins from year to year. If you look at an NBA team that has kept its personnel reasonably consistent -- for the purpose of exaggeration, let's use Utah -- you'll find it ranks about the same in most statistical categories from one year to another. Utah, for example, has been either first or close to it in assists and free-throw attempts since roughly the 15th century. The Celtics, for another, have been annual leaders in 3-point attempts ever since Paul Pierce and Antoine Walker joined forces.

Yet no such consistency exists for Expected Wins. Last year, for example, Dallas won 57 games despite just 52 Expected Wins -- the largest differential in the league. This year, with basically the same team, the Mavs have gone from winning five games more than expected to two fewer than expected (52 wins vs. 54 Expected Wins). They still shoot the lights out, commit few turnovers and play token defense just like they did last year, but now their ability to convert points into wins has suddenly changed.

Change of fortune
Wins vs. Expected Wins, last year and this year
  2001-02     2002-03 
  Wins  Exp. W  Diff.    Wins  Exp. W  Diff. 
Golden State  21  26  -5     33  33  0  
Seattle  45  49  -4     33  33  0  
Phoenix  36  39  -3     36  36  0  
Dallas  57  52  +5     55  53  -2  
Detroit  50  47  +3     44  43  -1  
Atlanta  33  30  +3     29  26  +3  
Chicago  24  21  +3     25  24  +1  
As the chart above shows, if you look at teams that fare unusally well (or poorly) compared to their Expected Wins, it almost never repeats itself. The only team to exceed their Expected Wins in both seasons is the Hawks, while all the others have shown no carryover from year to year.

And that, in turn, leads us to the conclusion that it's not an ability, but rather a fluke state. Luck, in other words.

The Celtics, then, have led a charmed life through this regular season. The Washington Wizards, for example, have been outscored by fewer than Boston, yet sit six games behind the Celtics in the win column in their battle for a playoff spot in the East. So it turns that the luck of the Irish may be what keeps Michael Jordan out of the playoffs in his final season.

John Hollinger covers the NBA for and is the author of Pro Basketball Prospectus.

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