The Nationals, hosting their traditional 11:05 a.m. July Fourth game, will try to avoid dropping their fifth straight game and falling below .500.
The Red Sox took an early 3-0 lead on the Nunez homer in the second inning, pulled away with a six-run fifth and saw Martinez cap the offensive explosion in the ninth. Martinez drove in four runs, increasing his major league-leading RBI total to 71.
"Just a good day," Martinez told mlb.com. "We came out, we kept the bases occupied, pretty much gave ourselves a chance where we kept passing the baton and getting the next guy up. Had a big hit from Bogey there early in the game, and everyone pretty much kept feeding off that."
Washington (42-42) matched Boston's hit total (12) but couldn't string them together or produce them at crucial moments. The Nationals remained seven games behind Atlanta in the NL East.
Washington's Tanner Roark (3-10) saw his June struggles bleed into July as he allowed nine runs on 10 hits in seven innings while preserving a tired bullpen. After the Nationals closed to within 3-2 in the fourth, Roark was tagged in the fifth.
"If these guys would give our lineup a chance, we'll start winning some games because we are playing better," Nationals manager Dave Martinez told mlb.com regarding the big inning. "I see that. We came back and scored two runs, and the energy was great. We go back out there, and they come back and score six runs, and everything just goes dormant again.
"They didn't quit, but here we go, scratching and clawing again, trying to get back in the game, and it's tough. It's tough for the boys."
Washington's hopes for salvaging the finale rest with right-hander Erick Fedde (1-3, 6.00 ERA), who is replacing injured Stephen Strasburg in the rotation. Fedde picked up a win in his previous start despite allowing five runs and eight hits in five innings of a 17-7 win over the Phillies on Friday.
"My stuff wasn't great today," he told MASN.com. "But days like those it's really nice when your team puts up 17 runs. I'll take that. Hopefully next time when the games are close, I can be the one to keep it close."
Wednesday will be Fedde's first career appearance against Boston.
Boston left-hander Eduardo Rodriguez (9-3, 4.11) will try to snap a two-start slump Wednesday morning. Last time out he gave up five runs on seven hits -- including two home runs -- in six innings of an 8-1 loss to the Yankees on Friday. It was his second straight loss after winning six straight starts.
"I missed a couple pitches down the plate and they made an adjustment," Rodriguez told the Boston Herald. "No matter who you face, if you miss on the plate that's what happens."
Rodriguez has never faced the Nationals.
The Nationals may get some offensive help Wednesday with the possible return of first baseman Matt Adams (fractured finger), who went 0-for-3 in a rehab game Tuesday night for Double-A Harrisburg.