Sophia Young and Becky Hammon stepped up for playoff-bound San Antonio and ended Washington's lost season with another loss.
Young scored 17 points and Hammon had 15 points and a season-high 11 assists to lead the Silver Stars to an 82-74 victory over the Mystics on Saturday night.
"We're the veterans of this team," said Young, who in her sixth season is the longest tenured player on the team. "Whenever things are going down, we have to be able to lead the team. I think our team is looking for us to do that. Whenever a team trusts us and knows that we are capable of leading them, that's important. That's what our team is developing into now."
Danielle Adams scored 14 points for the Silver Stars (17-16), who never led until the fourth quarter and won for the third time in four games. San Antonio, which will face Minnesota in the opening round of the playoffs, concludes the regular season Sunday at Tulsa.
Matee Ajavon scored 15 points and Monique Currie had 14 to lead the Mystics (6-28), who finished with their worst record since going 3-27 in their inaugural season in 1998. Jasmine Thomas and Nicky Anosike each added 10 points.
Washington lost 13 of 14 to close out the regular season a year after going 22-12 and tying for the best record in the Eastern Conference. The Mystics lost their last nine on the road, last winning July 17 at Los Angeles.
"We have played with a lot of heart, determination and resiliency for the entire season," Mystics coach Trudi Lacey said. "We're young, and we haven't been together very long at all. I think in tight games, experience truly helps. It shows when you don't have it."
The Silver Stars cut the lead to 58-57 heading into the fourth quarter, when Hammon's playmaking sparked the team.
Young scored 10 points in the fourth as the Silver Stars outscored the Mystics 24-17. Hammon, who joined San Antonio in 2007, had five assists in the period, finding Scholanda Robinson for a layup with 8:21 remaining to give the Silver Stars their first lead of the game, 61-60.
"We just take what they give us," Hammon said. "And if they want to pay me a lot of attention, then I'm going to find my teammates. They did a great job of spacing themselves and knocking down shots. We're very good when people knock down shots."
The Mystics and Silver Stars traded baskets until San Antonio went ahead for good on Robinson's 3-pointer with 6:55 remaining.
San Antonio hit 19 of 35 shots in the second half and outrebounded Washington 19-12. The Silver Stars had 23 assists and nine turnovers in the game, and the Mystics had 12 and 15.
Adams twice tied the game in the third quarter. The Silver Stars shot 10 for 18 in the quarter and forced five Washington turnovers. But after Adams' free throw with 2:10 tied it at 53-53, Anosike followed with a jumper and Ajavon hit a free throw.
Washington never trailed in the first half and led 41-34 at halftime. The Mystics held the Silver Stars to 13-of-35 shooting in the first two quarters and outrebounded them 24-13.
Currie led Washington with eight points in the first half and Ajavon had seven. Adams' nine points led San Antonio.
San Antonio cut a 12-point first-quarter deficit to 22-20 in the second when Adams completed a three-point play. But the Mystics again charged in front, matching the game's largest lead at 12 on Currie's jumper with 3:41 remaining.
Before the game, San Antonio announced that Hammon had signed a multiyear contract extension that's expected to keep her with the team for the remainder of her career.