So much for momentum swings.
The New York Mets have hit a tying home run with two outs in the ninth inning twice in the past two days — and lost both games.
"You'd like to at least win one of them, hopefully two, when you get that type of comeback and that momentum," Jason Bay said. "Unfortunately, it didn't happen."
New York nemesis Gaby Sanchez drove in two runs and singled to start the decisive rally. Stanton threw out Jose Reyes at the plate in the fifth, and Florida got seven strong innings from starter Javier Vazquez.
In the 10th, the Marlins took advantage of a defensive mistake by Daniel Murphy.
Sanchez and Hanley Ramirez singled with one out off Jason Isringhausen (2-1). Dewayne Wise followed with a single and went tearing toward second base, not realizing the runners had held up in front of him.
Murphy cut off the throw from right field and had Wise hung up between first and second. But the first baseman got preoccupied with the runner at third and flipped too late to second baseman Justin Turner covering first as Wise scrambled safely back to the bag.
"I was trying to make sure the run didn't score and I got caught in no man's land," Murphy said. "It changed the whole inning. It was a bad play on my part. I've got to get it in somebody else's hands."
The 21-year-old Stanton worked a full count against Isringhausen and hit a screaming shot to left for his second career slam and first this season. It was his 25th home run of the year.
Duda hit a two-run homer off closer Leo Nunez in the bottom of the ninth, snapping an 0-for-14 skid.
The Mets said it was the first time in franchise history they tied consecutive games on two-out homers in the ninth inning or later, citing research by the Elias Sports Bureau. Scott Hairston came through Sunday in Washington, but the Nationals pushed across a run in the bottom half to win 3-2.
"Just ups and downs. That's the game of baseball," said Bay, who homered in the fourth.
Nunez (1-2) got out of the inning and Burke Badenhop pitched a perfect 10th, handing the Mets their third straight loss following a five-game winning streak.
New York fell to 0-9 in the first game of a homestand.
"The whole thing was going 2-0 on Stanton. That was the worst thing I could've done there," Isringhausen said. "It was just 3-2, needed to throw a strike and got too much of the plate."
New York played its first home game since trading All-Star outfielder Carlos Beltran last week. Third baseman David Wright, who came off the disabled list July 22, was playing at Citi Field for the first time since May 8.
Angel Pagan got away with some foolish baserunning in the ninth when he slid headfirst into second with a one-out double, barely beating the throw. Stanton was slow to field the ball on what appeared to be a routine single, but with the Mets down by two, the wise choice for Pagan would have been to hold at first.
Bay grounded out before Duda drove a 1-1 pitch to center for his third home run, sending the crowd of 28,862 into a boisterous frenzy. Fans chanted Duda's name and he peeked out of the dugout for a quick curtain call.
"That was a great feeling," Duda said. "I think it's definitely a confidence-builder."
It was Nunez's fourth blown save in 34 chances.
"It is deflating a little bit, but you've got to give our guys credit the way they rebounded and came up with four straight hits," Marlins manager Jack McKeon said. "They didn't give up and say, 'Oh, tough luck.' We went right after them."
Sanchez went 2 for 3 with a walk, giving him a .390 career average against the Mets, the highest of any opposing player with at least 100 at-bats, according to STATS LLC.
Pelfrey, coming off a complete game at Cincinnati, threw 119 pitches over six innings and is 0-7 in 15 starts against the Marlins since beating them in his major league debut.
NOTES: Prized pitching prospect Zack Wheeler, acquired from San Francisco for Beltran, made his first start as a member of the Mets organization. He allowed four runs and seven hits in four innings for Class-A St. Lucie. ... Omar Infante got two of his three hits off Pelfrey, making him 15 for 26 (.577) against the right-hander. ... Mets manager Terry Collins said before the game that Murphy will get a day off Tuesday against rookie LHP Brad Hand. Hairston is likely to start in the outfield. Hairston came off the bench Sunday and homered twice. ... New York began a stretch with 20 of 29 games at home. ... Wright went hitless for the first time in 11 games since coming off the DL. ... The Mets opened a 10-game homestand, their longest of the season, after a 6-4 road trip. ... Reyes made a sensational play at shortstop to rob Emilio Bonifacio of a hit. ... In honor of Wright's return, the Mets are offering $5 seats in left field for this series.