Mike Stanton is a streaky hitter, and the Florida Marlins are happy to ride his power surges.

Stanton homered twice and drove in three runs to lead the Marlins over the Washington Nationals 6-5 Sunday for a three-game sweep.

"You can't really predict home runs, but that's what I'm expecting," said Stanton, who homered five times as the Marlins went 4-3 on a seven-game trip. "It's not like I'm going to say I'm hitting 45, 40 home runs every year, but if I just relax and have good at-bats for a full season, who knows how many I hit?"

At Double-A Jacksonville and the Marlins, the 20-year-old Stanton has homered a combined 41 times in 133 games. But he also slumped through an 0-for-31 streak in late August.

Stanton homered to left off Jordan Zimmermann (0-1) leading off the second, then hit a two-run drive in the third for 5-2 lead.

"He's going to continue to get better as he gets older and more at-bats," teammate Dan Uggla said. "It's kind of mind-boggling to see what he's doing at the age of 20. If we had brought him up at the beginning of the year, I think he could very easily have hit 30 or 35 — if not more than that."

Florida won 10 of its last 11 games against Washington to win the season series 13-5. The last-place Nationals have lost five in a row overall, falling a season-high 23 games under .500 at 60-83.

That caused Washington manager Jim Riggleman to close his clubhouse for almost a half-hour after the game so that he and coaches could speak to the Nationals about their effort.

"If anybody in the room thought that was acceptable, they need to be made aware that we certainly don't think it's acceptable," Riggleman said. "I think the losing wears on you, but it's a 162-game schedule. It's a nine-inning ballgame. That's what you sign up for. That's what you give."

Washington second baseman Adam Kennedy said the unconventionally delivered message was necessary.

"When you're in a situation like us and you have sloppy games, it looks twice as bad as it is. We don't have the luxury to go out there and take games, days off," Kennedy said. "We need to play clean baseball in order to win, in order for us to look good."

Chris Volstad, bidding to become the first Marlins pitcher to go 5-0 against an opponent in one season, allowed five runs — four earned — eight hits and three walks in 4 2-3 innings. He is to start a six-game suspension Monday, discipline assessed for his role in a brawl with Washington on Sept. 1.

"I felt pretty good today," Volstad said. "Eight singles — that's what they got. It wasn't like they were really ripping the ball."

Brian Sanches (1-2) won in relief, striking out four in 1 2-3 innings, and Clay Hensley got three outs for his third save in six chances, finishing 4 1-3 hitless innings for Marlins' relievers.

"I was confident the bullpen would keep us in the game, and they shut everything down," Marlins manager Edwin Rodriguez said.

Making his fourth start since returning from elbow ligament replacement surgery in August last year, Zimmermann received his first major league decision since a loss to the Chicago Cubs on July 18, 2009. He allowed five runs — four earned — five hits and three walks in three innings, throwing 80 pitches.

Ivan Rodriguez had three RBIs for the Nationals.

Florida took a 3-0 lead in the second on Stanton's homer, Emilio Bonifacio's run-scoring infield hit and an error Zimmermann on an errant pickoff throw that led to a run.

Rodriguez hit a two-run single in the bottom half. After Stanton's second homer, Ryan Zimmerman's RBI single cut Washington's deficit to 5-3 in the third. Uggla drove in a run with a fourth-inning groundout, and Rodriguez had an RBI grounder in the bottom half. Roger Bernadina's RBI single chased Volstad in the fifth.

NOTES: When Florida LF Logan Morrison walked in the second, it marked the 32nd straight game he has reached base with a hit, walk or hit by pitch. ... Marlins RHP Josh Johnson did not throw in the bullpen on Sunday and was ruled out of his scheduled start on Wednesday because of shoulder and back tightness. Manager Edwin Rodriguez said the team was leaning toward not having Johnson pitch again this season. A decision could be made Monday. "If there's any indication that he's not getting any better or that he's getting worse, it's my opinion that we should shut him down," Rodriguez said. ... Ron Menchine, the Washington Senators radio broadcaster who called the team's final game in D.C. in 1971 and criticized then-owner Bob Short for his plans to move to Texas, died Saturday. He was 76.