MIAMI -- Things had been going so well for the Nationals' offense before their current three-game series.

In its previous five games, Washington had averaged close to eight runs a night while cranking out 11 home runs and batting .281.

But there has been a thorn in the Nationals' side all year -- and it's coated in teal.

The Nationals' offense was stymied once again by the Marlins, this time by Josh Johnson, as Florida beat them, 4-2, in front of 16,307 on Saturday night at Dolphin Stadium.

With the loss, the Nationals dropped to a season-high 36 games under .500 and have now lost four in a row.

Against the Marlins, they are now just 2-12 this year. But manager Manny Acta believes that has a lot more to do with the Florida offense than whoever they have toeing the rubber.

"Power kills, and they have it," said Acta about the Marlins, whose run output was supplied by a couple of early home runs off Tim Redding, giving them 192 on the year -- 82 more than the Nationals. "They can hit. They can slug. They can outslug most of the teams in our league, and they're not even playing in a small ballpark, either.

"They can swing the bat."

And Johnson can pitch.

On the mound, the 6-foot-7 right-hander limited the Nationals to two runs on six hits in six innings while striking out a career-high nine and walking just one. Through the first five innings, Johnson kept the Nationals off the board and only allowed three hits.

"He throws a heavy ball," said Ryan Zimmerman, who had the only multi-hit game for the Nationals, going 2-for-3 with a run scored. "He throws that slider to righties, and he's a good competitor."

Redding wasn't as successful as Johnson early on.

The 30-year-old righty, making his team-leading 31st start of the year, gave the Marlins a four-run lead after the first two innings because of the only two pitches he wanted back. The first was a slider that hung up in the zone to Jorge Cantu in the first inning, which gave the Marlins a 2-0 lead. The second was a fastball that was supposed to run in on Hanley Ramirez, but traveled towards the middle of the plate and resulted in the star shortstop's 30th home run of the year, and a four-run deficit for the Nationals.

"I was just upset about two pitches," said Redding, who's now 1-3 with a 6.07 ERA in five starts against the Marlins this year. "Other than that, I was glad I was able to battle through another four innings.

"It kept us in the game, and the way we've been swinging [the bats], it isn't that much of a deficit."

But it was.

Redding only allowed a couple of singles in his next four innings, but the Marlins' early offense was enough to sink Washington because, for the second straight night, the Nationals' bats couldn't back their pitcher.

And it wasn't just Johnson. Down the stretch, four Marlins relievers pitched three hitless innings to hand the Nats another loss.

"Their bullpen came in and did a good job," Acta said. "You have to give them credit. But we never got anything going offensively tonight, and that's the difference."

Washington's only runs came with a two-out rally in the top of the sixth to shorten Johnson's night. With nobody on, Zimmerman and Lastings Milledge singled, and Elijah Dukes doubled high off the left-center-field wall to plate two. Over his last seven games, Dukes has now driven in 10 runs.

But Kory Casto -- who also made the last out of the game -- struck out when the Nationals had only their third runner in scoring position to end the inning.

In the ninth, the final backbreaker came on a double play by Dukes. After Marlins closer Matt Lindstrom walked Milledge to start the inning, Dukes rolled over on an 0-2 fastball that resulted in a 6-4-3 double play --which resulted in a bang-bang play at first base -- that pretty much sealed the deal.

"We just came up short," Milledge said. "Josh pitched a good game today, and it was tough to get runs."