Josh Willingham was 2-for-2 with a walk and two RBI, Adam Dunn collected two hits, scored twice and drove in a run and Adam Kennedy scored two runs, walked two times and had an RBI single for the Nats, whose lone loss in the last four games was a 4-2 setback in the opener of this three-game set Tuesday.
Luis Atilano (4-1) went 5 1/3 innings and held the Giants to a pair of runs on four hits to get the win.
Lincecum (5-1) was coming off his shortest outing of the year in a five- inning, five-run no-decision versus Arizona last Thursday. The two-time defending National League Cy Young Award winner dipped to 4 2/3 frames Wednesday and allowed a season-high six runs on six hits. He tied a season- high with five walks and struck out five batters.
"It's completely frustrating, but at the same time we have a lot of games. I don't want to be beat myself up over it, I have plenty of other outings to go through," Lincecum said.
Juan Uribe had a solo home run and Pablo Sandoval a run-scoring double in the loss, San Francisco's sixth in the last seven games.
Washington jumped on Lincecum for a three-spot in the third. Kennedy drove in Nyjer Morgan with a base hit after the latter led off with a single and swiped second. Willingham then doubled home Kennedy and Desmond connected for a two- out RBI single.
"We play every game the same exact way. You're on the other end of it at times too. In this league there is no easy win for any team," said Kennedy.
The pesky Nats were back at it in the fifth, as Kennedy drew a leadoff walk, stole his way to third and scored on a sacrifice fly by Dunn. Ryan Zimmerman, who walked between Dunn and Kennedy then stole second and Willingham was hit by a Lincecum pitch. Both advanced on a groundout and Desmond ended Lincecum's turn on the hill with a two-run base-knock to right for a 6-0 lead.
"You go out and play the game, you never know what's going to happen. We faced Lincecum and worked him pretty good, drew some walks and strung some hits together," Willingham said.
Denny Bautista came on and escaped without further damage and Uribe led off the bottom half with a home run to get San Francisco on the board. The Giants got another run back on Sandoval's double in the sixth, but Willingham countered with a run-scoring single an inning later.
Travis Ishikawa grounded into a run-scoring fielder's choice in the home seventh to cap the scoring.
The Giants placed shortstop Edgar Renteria on the 15-day disabled list prior to Wednesday's game with a strained right hamstring. Renteria left Tuesday's game in the seventh inning after attempting a sacrifice bunt. He had just come off the DL on Saturday after missing time with a strained right groin...Uribe and Aaron Rowandlogged multi-hit efforts for San Francisco...Lincecum threw 96 pitches, 56 for strikes.