Richmond scored 14 of his 30 points in the fourth quarter and the Wizards won in Seattle for the first time in 19 years, beating the SuperSonics 96-92 Wednesday night.
The Wizards, who had lost 18 straight games in Seattle, also got their first victory this season against a Western Conference foe.
The Wizards blew a late lead and lost to Indiana in the first game of their five-game road trip on Monday.
They squandered a 10-point, third-quarter lead against Seattle, which took an 81-80 lead on Gary Payton's layup. But the Wizards then made the big plays down the stretch.
Richmond was at his best in the fourth period when he was 5-of-6 from the field, including 3-of-4 from 3-point range.
"He made some incredible shots," Sonics coach Paul Westphal said. "I don't think it was bad defense as much as he just made some amazing shots."
His last 3-pointer was a 25-footer from the right wing with 6-foot-9 Billy Owens right on him. That basket gave the Wizards an 87-83 lead.
"We didn't have anything left as a team so Mitch put us on his back," said Washington coach Bernie Bickerstaff.
The Wizards (11-15) have 19 games remaining and 13 are on the road. With three games left on the current trip, the Wizards know they must win on the road to get into the playoffs.
"We need to string some wins together on the road to make a playoff run," said Otis Thorpe, who scored 18 points.
Rod Strickland added 10 points and 14 assists for the Wizards.
Calbert Cheaney's rebound basket gave the Wizards a 92-87 lead, but Owens then sank two free throws to make it 92-89 with 37.9 seconds left.
After Cheaney missed two free throws, Owens was fouled nd hit one of two free throws to cut the lead to 92-90. But Tracy Murray clinched the victory when he hit a 3-pointer for Washington with 7.4 seconds remaining.
Richmond made three 3-pointers in the fourth quarter, including one with 2:02 left that gave the Wizards an 87-83 lead.
The Wizards missed 7 of 12 free throws in the final period, but were 10-of-16 from the field.
The Wizards led by as many as 10 points in the third period, but Vladimir Stepania's dunk closed the deficit to 61-60. He was whistled for a technical foul for slapping the ball after his basket, though, and Richmond hit the free throw and then sank a 3-pointer as the shot clock expired to give the Wizards a 65-60 lead.
After Owens' basket gave the Sonics a 37-30 lead with 9:10 left in the first half, the Wizards took over. They outscored the Sonics 21-6 the remainder of the half for a 51-43 halftime lead.
Notes: The Sonics retired the jersey of Nate McMillan at halftime. A Sonics assistant coach, he spent all 12 years with Seattle and retired as the Sonics all-time leader in steals and assists. He joins Lenny Wilkens, Fred Brown and Jack Sikma as other Sonics players whose numbers were retired. ... John Crotty made his first appearance in a Seattle uniform and played 10 minutes in the first half. ... The Wizards nearly shot as well from the field as the free-throw line. They made 52 percent from the line (13-of-25) and 49 percent (38-of-77) from the field.
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