Jack McKeon's final series as manager of the Marlins began with a loss.
Earlier in the day, 80-year-old McKeon, the interim manager of the Marlins, officially announced that he will not return as skipper next season. Ozzie Guillen, who was released from his contract as manager of the White Sox Monday night, is reportedly in line to take over the Marlins next season as they move into a new stadium.
Marlins reliever Edward Mujica (9-6) worked himself into trouble from the start of the ninth. Pinch-hitter Laynce Nix and Ian Desmond singled, but Mujica struck out Rick Ankiel and induced a groundout from Ryan Zimmerman and could see his way out of the inning. But he left a splitter out over the plate and Morse made him pay for it with his 30th homer, a shot to left-center.
"Its tough, you think you're on the verge of closing one out, McKeon said. "The guys battled their tails off, we just couldn't finish it off."
McKeon took over the Marlins during the 2003 campaign, he led the team to a 75-49 record, a wild card berth and the World Series title with a win over the Yankees. He was named the NL Manager of the Year that season, marking his second such honor as he also won the award in 1999 with Cincinnati.
Atahualpa Severino (1-0) pitched a scoreless eighth for his first major league win and Henry Rodriguez finished off the Marlins in the bottom of the inning to nail down his second save of the year.
Rick Ankiel had two RBI and Desmond scored three times for the Nats, who have won three in a row and eight of their last nine.
"A lot of good thing happened," Nationals manager Davey Johnson said.
Florida got off to a good start for McKeon in the second frame when Morrison drove a high fastball from Nationals starter Tom Milone into the seats in right field for his 23rd home run of the season.
The Nats evened the game in the third thanks to a pair Marlins miscues. Desmond reached first on an error by Emilio Bonifacio, stole second, then took third on a balk by Marlins starter Anibal Sanchez before coming home on a groundout by Ankiel.
The Marlins took the lead in the third when Infante ripped a two-out triple and crossed the plate on a single to third by Mike Stanton that went off the glove of Zimmerman and into left field, but the Nats came back with a pair of runs in the fourth to take a 3-2 lead.
Wilson Ramos singled and came around to score two batters later on a double by Desmond, who then scored on a double by Ankiel.
Florida loaded the bases with one out in the fifth and were gifted the tying run when Nats reliever Craig Stammen uncorked a wild pitch, allowing Vinny Rottino to score.
The Marlins took the lead in the seventh with a two-out rally. Infante began things with an infield single and Mike Stanton drew a walk. Gaby Sanchez then came through with an RBI single to left.
Florida leads the season series with Washington, 10-6, including taking five of the last seven games between the teams...The start of the game was delayed 57 minutes by rain...Infante hit his eighth triple of the season...Milone gave up three runs on seven hits over 4 1/3 innings while striking out four and walking one...Sanchez lasted five frames, giving up three runs -- two earned -- on five hits.