Camille Little had 14 points and eight rebounds to lead the Seattle Storm past the Phoenix Mercury, 71-57, on Sunday.
Sue Bird added 13 points while Katie Smith and Shekinna Stricklen finished with 10 apiece for the Storm (16-18), who ended the regular season with three straight wins.
Seattle holds the final playoff spot in the Western Conference.
DeWanna Bonner netted 13 points to pace Phoenix (7-27), which dropped its final seven games.
Candice Dupree and Nakia Sanford each contributed 10 points in the loss.
The Mercury carried a 16-11 lead into the second quarter, but Seattle opened the frame with a 21-6 run and never looked back, holding at least a four-point lead for the remainder of the game.