Wednesday, September 9, 2009

Backs Against the Wall

The 100-82 loss by the Dream to the Mercury was the second game of a back-to-back. Let's look at all of the disadvantages that a team has playing back to back. (Note: I'm not trying to establish a narrative of "oh, we would have beaten the Mercury if we weren't playing the back-to-back" - the Merc have to play back-to-backs just as much as anyone else in the WNBA does.)

* A player's muscles are still retaining lactic acid from the night before.
* The player is flying across the country in a coach seat. Imagine a 6'4" woman crammed into a cattle car with wings.
* NBA players have chartered planes. WNBA players get to deal with crying babies in the seat behind.
* Time zone changes. Meaning little or no sleep.
* Bad food.
* Little time to prepare for the game.

We can make guesses about how a team is affected by a back-to-back game - but what really happens? Are teams playing on a back-to-back significantly worse? What are there average margins of victory? Does it matter if the second game of the back-to-back is at home or on the road?

I took at look at every game in the WNBA for the 2009 season which was either:

- the second game of a back to game, or
- the third game in four nights, which can be just as bad. Those games are the fourth game in the game-game-off-game sequence, else they'd be counted as just ordinary back-to-backs.

There are 53 such games this year in the WNBA. Fifty have been played, three are left to play. First, let's see how many such games each team will end up playing:

Chicago: 6
Connecticut: 6
Washington: 6
Los Angeles: 5
Minnesota: 5
Atlanta: 4
Detroit: 4
New York: 4
Sacramento: 4
Indiana: 3
Phoenix: 2
San Antonio: 2
Seattle: 2

To add insult to injury, for the Silver Stars and the Storm one of those two "back-to-back" games is actually the third game of a game-game-off-game series, adding a slight cushion of rest.

Did the WNBA schedulers put this fix in for San Antonio or Seattle? Probably not. One can guess that schedules have to do a lot with arena availability and travel conditions - but the Silver Stars and Storm probably smiled when they looked at
their schedules.

Next up: the average margin of victory for these teams on back-to-back games:

Phoenix: 13.50
Detroit: 13.00
Los Angeles: 3.40
Seattle: 1.50
Connecticut: -0.17
Indiana: -2.00
Sacramento: -2.75
Washington: -4.80
New York: -5.50
San Antonio: -8.00
Minnesota: -11.20
Chicago: -12.00
Atlanta: -12.67

Average: -3.20

On the average, it seems that playing that back-to-back game can take three points off your average. Since the best teams (Indiana, Phoenix) are winning by 3.81 points per game and 3.75 points per game respectively, a back-to-back team can turn a good team into an average team and an average team into a horrible one.

Note that some teams come out quite well in the average because either:

a) they got hot when they were having most of their back-to-backs (Los Angeles),
b) played a small sample size of games (Phoenix), or
c) had big wins that skewed the average (Detroit).

The next question: how do back-to-backs impact the win-loss record of a team:

Back-to-Back Win-Loss Records
(includes Game 3 of game-game-off-game series)

Record: 21-29, .420
Home: 11-4, .733
Away: 10-25, .286

It looks like that when it comes to playing a back-to-back game, knowing that you're going to play that game at home helps. Even when playing those back-to-back games, teams playing them at home win almost 3 out of 4 times. However, teams playing back-to-back games on the road lose 1 out of 4 times.

I then looked at the mathematical correlation between the number of back-to-backs played by a team and its winning percentage. You'd expect an "inverse correlation" - the more back-to-backs, the greater the negative impact on winning percentage.

The correlation is -0.47122, which is a medium correlation - and veering into large territory. So do lots of back-to-back games cause bad records? No. Correlation does not equal causation - the two factors might be related to an unknown third factor. However, it is something to think about as we come into crunch time at the end of the seasons:

Final Back-to-Backs of 2009 WNBA Season

September 10, Detroit plays Game 2 of Back-To-Back: opponent New York
September 12, Atlanta plays Game 2 of Back-To-Back: opponent Washington
September 13, Washington plays Game 2 of Back-To-Back: opponent New York.

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