Washington (12-8) has lost two straight, allowing 203 points in the losses.
The latest came Wednesday at home when the Atlanta Dream beat the Mystics 106-89.
Atlanta shot 60.3 percent from the field and made 11 of 18 shots beyond the arc. Washington trailed by nine at halftime and pulled within seven early in the fourth quarter, but Atlanta's Angel McCoughtry scored six straight points to push the lead to double digits.
"Most nights when you score 89 points you should probably win," Mystics coach Mike Thibault told the Washington Post. "But when you play defense as badly as we did, you dont give yourself a chance to do that."
Natasha Cloud led the Mystics with 17 points and Elena Delle Donne added 16 points and nine rebounds.
Chicago (7-13) gave up just under 100 points Tuesday night in a 98-74 home loss to the Las Vegas Aces.
The Aces closed the third quarter with an 18-2 run to take a 76-50 lead. The Sky got no closer than within 17 points in the fourth quarter.
The Aces outscored the Sky 59-29 in the second and third quarters. Las Vegas made 47.9 percent of its shots from the field compared with 38.0 percent for the Sky.
Diamond DeShields had 15 points to lead Chicago.
Chicago is allowing the most points per game (88.2) in the WNBA and the Mystics the fifth most (82.7). Offensively, the Sky lead the league in 3-point shooting percentage (36.9) and the Mystics are third (35.8). Chicago is averaging 15.4 turnovers per game, the most in the league.
Washington won the first two meetings this season.
In the first game, the Mystics pulled away with a 17-2 run in the third quarter en route to an 88-60 victory June 19. Kristi Toliver led Washington with 19 points. Cheyenne Parker scored 18 for Chicago.
Their second meeting of the season three nights later featured Delle Donne's return to Chicago. She scored 22 of her 30 points in the first half in Washington's 93-77 victory, adding 10 rebounds, six assists and two blocks. Allie Quigley scored 21 points for the Sky.
Despite Washington's recent losses, the Mystics are only 2 1/2 games out of first place overall.
"Every game is a dogfight, so you've got to be ready to fight it out like a playoff game," Delle Donne told the Post. "It's definitely wide open. I feel like the standings don't mean a thing right now."