Morse hit his 30th home run, a three-run shot with two out in the ninth inning, to rally Washington past the Florida Marlins 6-4 Monday night.
The hit boosted Morse's average to .303, helping his bid for his first .300 season. The native of Fort Lauderdale, Fla., earned a curtain call from friends and family seated behind the Nationals dugout.
"This was great," he said. "The curtain call was unreal, and to help the team win today, it was a big game."
The Nationals clinched third place in the NL East. They're the first team from Washington to finish as high as third since 1945.
With two games remaining, the Nationals (79-80) still have a chance at the franchise's first winning season since 2003.
"We haven't accomplished anything unless we're fighting for a pennant," manager Davey Johnson said. "We're moving in that direction."
Washington improved to 16-9 in September.
"A lot of these guys wish there was another month left," Morse said. "We're jelling together and pushing forward and showing teams that we can turn this division around soon."
His homer came off Edward Mujica (9-6), who was trying to earn the first save for the Marlins since closer Leo Nunez returned last week to his native Dominican Republic and admitted playing under an assumed name.
The game marked the start of the final series at the stadium the Marlins are leaving for a new home near downtown. Two games remain in the stadium that has been their home since their first season in 1993.
Jack McKeon announced before the game he'll retire as Florida's manager at the end of the season after a three-month career comeback at age 80. The defeat dropped his team deeper into last place in the NL East.
"Tough one," McKeon said. "I thought we had it in the bag. I guess it's one of those years."
Florida's Anibal Sanchez needed 104 pitches to get through five innings in his final start. He allowed three runs, two earned, and walked five.
"Something really weird happened with my mechanics," Sanchez said. "That's not the way I wanted to finish the season."
The Marlins took a 4-3 lead in the seventh. Omar Infante reached on a two-out infield single, Mike Stanton walked and Gaby Sanchez followed with an RBI single. Washington then came from behind for the third time.
The final series in the ballpark notorious for wet weather got off to an appropriate start with a 57-minute rain delay.
Florida took a 2-1 lead in the third when Infante tripled and scored on a single by Stanton.
The Nationals went ahead 3-2 in the fourth thanks to an RBI double by Desmond and a run-scoring single by Ankiel.
Washington's Craig Stammen retired all five batters he faced, but his wild pitch allowed the tying run to score in the fifth.
Marlins RHP Javier Vazquez takes a streak of 25 consecutive scoreless innings into his final start Tuesday. The start could be the last for Vazquez, 35, who says he's leaning toward retirement. ... Miami native Chris Marrero drew a big cheer when he singled for the Nationals in the eighth inning. ... The Marlins chose RHP Michael Brady as their minor league pitcher of the year and OF Christian Yelich as their minor league player of the year. ... With a single, Jayson Werth improved to 4 for 27 against Anibal Sanchez. ... Sanchez's balk was his fifth, most in the majors.