Looking at the 2013 data, it's hard to say how rest affects WNBA performance. We only have 89 games to look at in the 2013 WNBA season. Here is the list so far:
|Days Since Last Game?||W||L|
Note that "0" days since the last game means that this was the opening game of the season. The record is not .500, since some teams opened against teams that already played games.
Furthermore, there is the complication that two teams in a matchup will have had the same number of days of rest. If one team is on three days rest and that team plays a team also having three days rest, after the match we had a "win" in the three days rest column and also a "loss", since both teams having had three days rest cancel each other out when they meet (get it)?
Having one days rest is detrimental. The only two wins off one day of rest were an 85-80 win by Washington over Minnesota at home after beating Connecticut on the road the previous night and an 84-48 blowout by Los Angeles over San Antonio at home after losing in Phoenix by 16 the night before.
There is also the theory that too much rest will hurt you. Note that of the three teams that had nine days of rest, all of them lost.
6/23/2013 - San Antonio 78, New York 77. The Libs had nine days of rest. They could have pulled this one out, but missed their last three shots.
7/9/2013 - Minnesota 94, Atlanta 72. Atlanta was the team coming off nine days of rest. After this game, Sancho Lyttle had foot surgery.
7/11/2013 - Los Angeles 94, Tulsa 78. Los Angeles got a road win over well-rested Tulsa.
The theory is that there is an "optimal rest period" for a WNBA team. Not too short, but not too long. I don't think there are enough data points to prove anything, but the current season results look promising.