Mets starter Chris Flexen, making just his fifth career start, threw a breaking ball that stayed elevated in the zone. Realmuto made him pay for it.
"Fortunate to get out there and get some runs for our pitching," Realmuto said. "I hadn't faced that guy before. He left a curveball out over the zone. I was able to put a good swing on it."
With the win, the Marlins have won six of seven and at 59-61, they're two games under .500 for the first time since being 12-14 on May 3.
"The main thing is, we keep playing," Marlins manager Don Mattingly said. "Just keep playing, you feel like you've got a chance to win every day, no matter who you're throwing out there and what's going on. For us, it's trying to focus on winning a series."
Flexen submitted one of his strongest starts of the season following a one-hour, 58-minute rain delay, limiting the Marlins to just those three runs in 5 1/3 innings.
In three of his five starts this season, Flexen has walked four batters, and two of his free passes came around to score Friday. On the offensive side, the Mets' bats stayed quiet and could not mount a comeback against Nicolino and a quartet of Marlins relievers.
On the heels of just being swept in the Subway Series, and acknowledging that outfielder Curtis Granderson was on the move to the Dodgers in a postgame trade, Mets manager Terry Collins admitted the team may have been flat.
"When you come off a series as electrically charged as it was the last four days, even though we didn't win games, the energy in the ballpark was tremendous," Collins said. "And all the rumors that are still flying, yeah, the air might have been out of the balloon tonight a little bit."
Sitting on a Major League-leading 44 homers, Stanton finished 0-for-2 with two walks, seeing a total of eight balls and four strikes in his first two plate appearances.
MOMENTS THAT MATTERED Get Real: Flexen paid for a leadoff walk in the second inning, when Realmuto clobbered a hanging curveball 402 feet over the left-field fence for a two-run homer. The blast gave Realmuto a career-high 50 RBIs.
"Fifty is really not that many," Realmuto said. "I've never been a huge RBI guy. I'm happy to cross that 50 mark. Hopefully, I've got 20 or more in me this year."
Flexen his muscle: After giving up three early runs, Flexen settled down to retire eight of the next nine batters he faced. The rookie did not face trouble again until the sixth, when he walked Ozuna and allowed a one-out hit. The Mets turned from there to reliever Josh Smoker, who earned a key out when Wilmer Flores made a sprawling catch of Tomas Telis' popup.
Smoker then induced an inning-ending groundout to preserve Flexen's final line.
"I thought I did a good job of limiting the damage tonight, held them to three runs, got out of a couple jams," Flexen said. "I thought I executed a game plan on certain guys, and I think the biggest thing that hurt me was just the breaking ball on the plate that got hit out."
"We'll keep marching down the road. Obviously, you've got to get back to .500 before anything can happen." -- Mattingly, on Miami getting to the shadows of a .500 record.
"This is hard for these guys. We started Spring Training with tremendous expectations, and they all had it themselves, too. To have, all of a sudden looking around, there's new people everywhere. I think it's a little bit of a culture shock for some of those guys." -- Collins, on the Mets' recent trades.
SOUND SMART WITH YOUR FRIENDS Realmuto had 48 RBIs last year. A Marlins catcher has reached as many as 50 RBIs in a season just 10 times, and the all-time leader is Ivan Rodriguez, who drove in 85 in 2003.
TAKE ANOTHER LOOK The Marlins won a replay review in the fourth inning after Matt Reynolds hit a ball that ricocheted off Nicolino's glove to second baseman Dee Gordon, who made a barehanded play and throw to first. On a close call, Reynolds was ruled safe at first. Miami challenged, and after a review of one minute, 48 seconds, the call was overturned.
WHAT'S NEXT Marlins:Vance Worley (2-2, 4.97) makes his ninth start and 17th appearance on Saturday in the second of three games against the Mets at Citi Field. The first pitch is set for 7:10 p.m. ET. Worley is 4-4, 5.59 ERA in 48 1/3 innings against New York.
Mets: Coming off one of his best outings of the season, Rafael Montero (1-8, 5.80 ERA) looks to pitch well enough to retain his rotation spot when the Mets return to Citi Field on Saturday against the Marlins. Despite allowing two runs in six innings last time out, Montero has gone eight consecutive outings without a win.