MIAMI -- A steady rain and the Washington Nationals combined to dampen Florida's playoff hopes.
The game was called after a 53-minute delay in the bottom of the ninth inning. The Marlins had a runner on base with nobody out.
Rain also halted play for 2 hours, 10 minutes in the sixth.
Lannan (9-11) allowed one run and six hits in five innings. He did not return after the first delay. It was his first win since Aug. 5, also against Florida.
"I'm pretty happy with today," Lannan said. "I wish the rain didn't come but I'm glad we got the win. I was locating my fastball, my curveball felt good today. The Marlins are a good team. Taking two of three from them is big for us."
The Marlins, who had won four of five, remained 5 1/2 games behind Colorado for the NL wild card. The Rockies lost 7-3 at San Diego.
Last-place Washington won for the third time in four games.
"We know we are not going anywhere in the standings, but the guys are playing with intensity, they are playing hard and I appreciate that," Nationals manager Jim Riggleman said. "Just some great individual efforts."
Florida starter Chris Volstad (9-12) gave up five runs -- four earned -- and five hits over three innings while walking five. It was his 28th start of the season, but first since being recalled from Triple-A New Orleans on Tuesday. It also was his third consecutive loss at the major league level.
"Five walks in three innings is not me. That's definitely trouble," Volstad said.
The Nationals scored three runs in the first, aided by a Marlins defensive gaffe.
Willie Harris walked and Ian Desmond singled to put runners on first and second with no outs. Cristian Guzman hit a soft grounder and second baseman Dan Uggla missed the tag on Desmond before making a high throw to first for an error.
Harris scored on a wild pitch, and Elijah Dukes' two-run single made it 3-0.
The Nationals stretched their lead to 5-1 on Orr's two-run homer off Volstad in the third. Orr, who played for Washington in 2008, was called up from Triple-A Syracuse on Aug. 28.
"He was struggling with his command," Orr said. "He left the ball a little bit up and I took advantage."
Guzman singled in Harris in the fourth off reliever Andrew Miller to make it 6-1. Orr scored on a groundout in the fifth.
Cody Ross singled in Uggla in the eighth to make it 7-2.
"Tough series for us. Definitely not what we wanted," said Ross, adding that the rain wasn't a factor in the loss. "When you're losing the whole time it just makes it miserable. The steady rain just compounds that terrible feeling you have inside."
Dukes has reached base safely in 17 consecutive games. He returned to the lineup after missing Saturday's game with a stiff lower back. ... Justin Maxwell hit two solo homers as Duke's replacement Saturday and remained in the starting lineup Sunday. ... Ryan Zimmerman and Josh Willingham were both given Sunday off "to clear their heads," Riggleman said. ... Ramirez's streak without an error at SS ended at 56. ... Ramirez needs one RBI for his first 100-RBI season.