2011: Disappointing Seasons and the Expected Wins Method

by James Bowman on Sep 9, 2011 4:21 PM EDT

One way of rating basketball coaches is something called the Expected Wins Method which was created by John Hollinger (like so many other great ideas in basketball statistics). The idea behind evaluating a coach is to compare the total number of wins a coach achieves during a seson against the expected wins for the team.

In order to figure out a team's expected wins, we need to know the expected win percentage. He defines this value as

expected winning percentage for a team = (0.25)*(winning percentage of season before last) + (0.5)*(winning percentage from last season) + (0.25)*(.500)

In short, the number of wins that should be expected in a current season is weighted:

50 percent of the performance one year before
25 percent on the performance two years before
25 percent on a hypothetical .500 season - the purpose to give the coach of a sub-.500 team something to strive for, and to give the coach of a winning team a reward for continuing to win.

Below are the expected wins for each team in 2011. Following in parentheses is the number that has to be either subtracted (-) or added (+) to the number of expected wins to get the team's current win number. Teams that are overperforming will have plus values and teams that are underpeforming will get the minus values.

Comparison of Expected Wins to Current Wins for 2011

Seattle: 23 wins (-4)
Indiana: 20 wins (+1)
New York: 19 wins (-1)
Washington: 19 wins (-13)
Atlanta: 18 wins (+1)
Phoenix: 18 wins (+1)
Connecticut: 17 wins (+3)
Chicago: 15 wins (-1)
Los Angeles: 15 wins (-2)
San Antonio: 15 wins (+1)
Minnesota: 14 wins (+12)
Tulsa: 12 wins (-9)

If we look at the above numbers and compare them to Mechelle Voepel's ESPN article on which teams had the most disappointing seasons, the leader would be Washington, which was expected to win at least 19 games this year but has only won six. Tulsa comes in second because frankly, Tulsa wasn't very good last year and it's harder for them to "fall away" from the expected wins total of 12 wins. Third place would be Seattle - the idea going into 2011 was that the Storm would repeat at Western Conference champion, but it just didn't turn out that way.

What's the antonym of disappointing? Satisfying? In that case, the most satisfying team for their fans is Minnesota, which might get that visit to the WNBA Finals after waiting so long. Their 26 wins (so far) is great for a team expected to win just 14 games by this method. There really is no clear second place finisher, but if Connecticut wins their final game of the season I think they'd be the favorite.

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Comments

Nice work

My one concern: How might something like this account for drastic personnel changes?

It’s hard to shape expectations for Washington in 2011 with their success in 2010 because they were such a different team this year.

Twitter: @NateP_SBN.

by Nate Parham on Sep 9, 2011 5:53 PM EDT reply actions

Personnel changes

and injuries.

by ttdomi on Sep 10, 2011 3:26 PM EDT up reply actions

Yeah, this is one of those cases where this sort of statistic has a limited applicaiton

It’s an interesting reference for teams that held reasonably steady in terms of personnel the last few seasons, but you sort of have to throw it out the window for everyone else.

If Minnesota had been healthy last year, their expected wins for this year would have been much higher. That having been said, I do agree with this: "In that case, the most satisfying team for their fans is Minnesota, which might get that visit to the WNBA Finals after waiting so long. " Ab-so-freaking-lutely.

by Shannon Cotterell on Sep 12, 2011 2:24 PM EDT up reply actions