MIAMI — Giancarlo Stanton needed all of his considerable strength to maintain a stoic expression after he overcame his own baserunning blunder by crawling back to third base.
When Stanton scored moments later and reached the dugout, he finally allowed himself a big grin.
The Miami Marlins were a laughingstock for the first two weeks of the season, but they're all smiles now. Adeiny Hechavarria hit a bases-loaded triple after a botched rundown saved Stanton and kept the inning going, and Miami completed its first three-game sweep of the Washington Nationals since May 2012 by winning 6-2 Sunday.
"When we play our way, when we play relaxed and loose and confident, we're as good as anybody," manager Mike Redmond said.
The Marlins earned their fifth consecutive victory after a 3-11 start. Meanwhile, the defending NL East champion Nationals (7-12) lost their fifth game in a row — their longest skid since July 2013 — and fell behind Miami into fourth place in the division.
"We surely didn't want to start like this," said Bryce Harper, who hit his fifth homer. "We're a great team, and we'll get it going."
Stanton hit an RBI triple off the top lip of the center field wall, reached on an infield single and scored twice. Miami hit three triples in a game for the first time since 2000.
Washington's Gio Gonzalez (1-2) allowed 10 hits and six runs in five innings, hiking his ERA to 5.01. The left-hander had won his past five starts against Miami, his hometown team.
Dee Gordon, who came into the game leading the NL with 28 hits, had four singles for Miami and raised his average to .390. Ichiro Suzuki had two hits, including an RBI single, and is batting .304.
Miami outhit Washington 14-4.
Dan Haren (2-1) needed 91 pitches to get through five innings but allowed only two runs, including the sixth homer he has given up in 24 innings this year.
The 6-foot-6 Stanton hustled to overcome his baserunning mistake with two outs in the fourth. He tried to score from second base on an infield single, and got hung up 30 feet from the plate.
Catcher Wilson Ramos chased him all the way back to third, pumping but never throwing, and Stanton made an awkward headfirst dive and then crawled to the bag.
"I dove a little early and I still didn't get tagged, so I crawled," Stanton said. "I shouldn't have been in that situation, but luckily I was able to get out of it, and Hech came up clutch.""
The bizarre sequence loaded the bases, and the Nationals — who rank last in the majors in fielding — paid for their mistake when Hechavarria tripled to put Miami ahead, 3-1.
Ramos declined to talk to reporters.
"I don't know why Willie didn't give the ball up, but he decided not to," Nationals manager Matt Williams said. "The big inning was the result of us not executing."
Hechavarria started the season 1 for 22 but has since batted .460 since. He ranks among the major-league leaders with 16 RBIs.
"I feel great at the plate right now," Hechavarria said.
The sweep in the first meeting of the year between the division rivals was a big turnaround after Washington won 13 of 19 against Miami last year.
Stanton's triple, only the ninth of his career, traveled about 415 feet to spacious center field.
"You never know with center field here. It's like the Everglades," he said. "If I ever want to go for the cycle, now I know where to hit it."
The Marlins' retractable roof hasn't been open since their rain-delay gaffe opening day. It was closed Sunday not because of rain, but because of heat — 94 degrees at game time.
Nationals RHP Max Scherzer tested his sore right thumb by throwing off flat ground, and said he's uncertain whether he'll make his next start as scheduled Tuesday at Atlanta.
Nationals: RHP Doug Fister (1-0, 2.37) starts Monday in the opener of a three-game series at Atlanta against Eric Stults (0-1, 4.50).
Marlins: RHP Jarred Cosart (1-1, 3.63) starts Monday when they begin a three-game series against the Mets and Dillon Gee (0-1, 5.60). The Mets swept Miami in a four-game series a week ago.