Bryce Harper (0-for-4) crumples to the ground after fouling a pitch off his left ankle Wednesday in Miami. Harper’s nine-game hitting streak came to an end as well, his last hitless outing coming May 19 vs. Baltimore. (Sarah Glenn/Getty Images)

Chien-Ming Wang climbed the Marlins Park mound Wednesday night, his first start of the season presenting dual missions. He could prevent the Washington Nationals from being swept, and he could add clarity to the suddenly muddled back end of their starting rotation. With no outs in the fifth inning, Wang stood tall in the middle of the diamond, neither aim fulfilled, as Manager Davey Johnson limped out to take the ball.

Wang had faced 22 batters, and 12 reached base. He did not record an out past the fourth inning. He watched Ross Detwiler state his case to take back the fifth starter spot. And after a 5-3 loss to the surging Miami Marlins, the Nationals packed their bags for the flight back to Washington, the sour end of a trip that started so perfectly.

The Nationals began a nine-game trip May 21 that would define their early-season standing in the National League East. They bested the Philadelphia Phillies, steamrolled the Atlanta Braves and then arrived here, at a new stadium that packs familiar horrors. After the Marlins swept them, the Nationals are 18-39 in South Florida since 2009. The Nationals remained in first place, but their lead over Miami, the healthiest team in a MASH-unit division, dwindled to half a game.

“We hit a hot team at the wrong time,” Detwiler said. “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.”

The Nationals did not leave Miami without a fight. Adam LaRoche led off the ninth inning off embattled closer Heath Bell with his second double, a rocket to right field. Ian Desmond grounded out, and Danny Espinosa struck out. Roger Bernadina walked, which put the tying run on base for pinch hitter Rick Ankiel. Bell struck out Ankiel looking at an outside fastball to end it.

“If you look at the road trip, we did all right,” said Espinosa, who went 2 for 4 with a triple and an RBI single. “It’s tough to play on the road, a new stadium. It doesn’t feel good to get swept, but if you look at the overall picture, we did play well on the road.”

The Nationals still finished their swing through the NL East at 5-4, a record they would have taken when it started, but that seemed like a missed opportunity after the finish. They will return to Nationals Park with a question: Should their fifth starter be Wang or Detwiler?

Wang is “in the rotation,” Johnson said. “He’s replacing a guy that threw the ball pretty good for me. But I like the upside of Chien-Ming, and we’ll just play it by ear as it goes.”

Recovered from his spring hamstring strain and back in the rotation, Wang allowed four runs in four innings. He fired his sinker in the low 90s and flashed an effective slider, but his command was lacking. His sinker stayed up enough for the Marlins to smack seven hits. Wang struck out four batters, an unusually high number for him, but he also walked three and ended his night by hitting Giancarlo Stanton in the forearm.

Johnson felt Wang was “rusty,” having not started in the majors all year. Through an interpreter, Wang explained he felt off with the “tempo” of his delivery. He opened his front shoulder too early, causing the ball to stay up and his sinker to sink less.

“I’m kind of disappointed in myself today for the performance,” Wang said. “I’m trying to get adjustments in the bullpen session for the coming days.”

Detwiler relieved Wang — the inverse of what occurred five days earlier in Atlanta — and tossed two impressive frames, blowing his 95-mph fastball past several Marlins. After four uneven starts, Detwiler pitched with more aggression and, coming out of the bullpen, with fewer thoughts racing through his head.

“The way I look at it is, I’m a little off right now,” Detwiler said. “I just need to go out there and get myself right. I have no control if I’m going to start or be in the bullpen. If I go out there and get myself right, pitching my best, it puts it in other people’s hands.”

The Nationals built a 3-1 edge behind Espinosa and Bernadina. Espinosa responded to Johnson’s insistence he alter his approach at the plate. Bernadina drove in two runs and bailed Wang out of a bases-loaded, one-out jam with a tremendous throw from right field on a would-be sacrifice fly.

At moments, Wang looked like the sinker-baller the Nationals wanted in their rotation. In the third, Omar Infante corkscrewed himself into the ground and nearly fell over while whiffing on a 93-mph sinker for strike three. Wang ended the inning by striking out Stanton, one of the hottest, more fearsome hitters in baseball, taking a flat-footed swing at a slider that darted away from him. (Stanton would later continue his abuse of Nationals pitching with a homer in the seventh off Ryan Perry.)

“His stuff was good,” Johnson said. “But his command was off.”

Pitching with a 3-1 lead, Wang began the fourth inning with two walks, eight balls in nine pitches. Pitching coach Steve McCatty trudged to the mound and Detwiler began warming in the bullpen.

After a groundout pushed the runners to second and third, Chris Coghlan swatted a sacrifice fly to left and Marlins starting pitcher Josh Johnson poked a broken-bat single to center. Wang had walked the first two hitters of the inning, then allowed them to score while facing the eighth and ninth hitters, losing the lead in the process.

Wang started the fifth by yielding a laser of a single to Hanley Ramirez. When he hit Stanton, Johnson decided he had seen enough. In came Detwiler, who tried to squeeze out of the jam. He whiffed Logan Morrison with a 95-mph fastball. But he walked Bryan Petersen to load the bases.

John Buck followed with a groundball that seemed destined for left field — until Ryan Zimmerman made a breathtaking, diving stop. From his knees he threw to second, but the ball sailed wide. Everybody was safe, and the Marlins led 4-3.

The Nationals had lost the lead, and soon they would lose the game. They headed back to Washington, still in first place, with an off day and, perhaps, the return of Michael Morse awaiting. Even with Morse’s impending debut, the Nationals’ luck had not changed — Johnson revealed that reliever Henry Rodriguez had slammed a bathroom door on his finger. He may or may not be able to pitch Thursday.

“It’s not fun to get swept,” Johnson said. “But we’ll show up Friday.”