"It happens, but overall I think if you look at the road trip, we did all right," second baseman Danny Espinosa said. "It doesn't feel good to get swept."
Wang, who missed the Nats' first 42 games while rehabbing from a left hamstring injury, gave up a run early, when Giancarlo Stanton drove in his 38th run of the year with a single in the first inning.
Despite the early damage, Wang got some help from Espinosa and Roger Bernadina to keep things close.
After Espinosa tripled to open the second, Bernadina tied the game with a sacrifice fly off Marlins righty Josh Johnson, and then saved a run in the bottom of the frame with a great throw from right field to help Wang escape a bases-loaded, one-out jam. Jose Reyes hit a fly ball to Bernadina, who delivered a strike to Jhonatan Solano at the plate to prevent Bryan Petersen from scoring.
Bernadina did more damage at the plate in the fourth when he followed up Espinosa's RBI hit with an RBI double to make it 2-1, but he was thrown out at third trying to stretch the hit into a triple.
Wang wasn't able to escape unscathed from another jam in the fourth, though, as the Marlins sent seven men to the plate and scored two more thanks to back-to-back RBIs from Chris Coghlan and Johnson. Wang gave up a leadoff double to Ramirez in the fifth, and then hit Stanton with a pitch to end his night. Hanley Ramirez eventually scored on a John Buck infield single off lefty Ross Detwiler to put the Marlins on top.
"I'm kind of disappointed in myself today for my performance," Wang said through his translator. "I'm going to try to make adjustments in the coming days."
Despite Wang's struggles, Nats manager Davey Johnson said he plans to stick with the hurler every fifth day instead of inserting Detwiler back into the rotation, but will see how it plays out down the line.
"He's in the rotation," Johnson said. "He's replacing a guy who threw the ball pretty good for me, but I like the upside of Chien-Ming. ... I know I'm going to get those questions, but Chien-Ming is a quality pitcher and obviously he had some rust on him."
In the seventh, Stanton belted his 12th home run of the month to stretch Marlins' lead to 5-3.
The Nats were unable to climb back into the game, as Johnson finished with six solid innings before the Marlins' bullpen completed the final three frames. After Bernadina's fourth-inning double, Miami pitchers retired 13 of the next 14 batters, and Marlins closer Heath Bell struck out Rick Ankiel to end the game with runners on the corners and send Washington into Thursday's off-day with three consecutive losses.
"Things are finally coming together as they should," Stanton said after the Marlins finished the winningest month in club history. "Long overdue. It seems these games we can finally show how good we are."
Despite being swept and seeing their lead NL East diminish, the Nats finished their nine-game road trip with a winning record at 5-4, as they return home for a six-game stretch.
"It's definitely tough," Detwiler said. "We hit a hot team at the wrong time, but we're still in first place. We have to go out there Friday and say, 'We're still in first place, we're still the team to beat.'"