Thanks to a drop of an easy toss to first by Miami reliever Mike Dunn, the Nationals rallied for six runs in the eighth and went on to beat the Marlins 10-7 on Saturday night.
Washington stretched their lead in the NL East to three games over the Braves.
"It's a tight race," outfielder Bryce Harper said. "The Braves are playing well. We're playing well. When we win, they win. It's going to be tough to keep this going."
The Nationals overcame three errors -- two by Espinosa, who broke a 1-for-20 slump with two hits and his 10th home run of the season.
"It started out a very sloppy game on our end, really for the majority of that game," LaRoche said. "To turn it around like that, it says something about this club. Not that we should be surprised. We've been doing it all year.
"They took advantage of every mistake we made. They stole a bunch of runs. It wasn't looking good. That was a huge inning."
Washington trailed 6-4 heading into the eighth, but the Nationals tied it on run-scoring singles by Steve Lombardozzi and Tyler Moore against Dunn (0-1). Dunn allowed six runs -- all unearned -- but his error caused the damage. He dropped Carlos Lee's toss on LaRoche's ground ball with one out.
Miami manager Ozzie Guillen delivered an expletive-laden tirade when asked about Dunn's error.
"There you go," he said. "There's the baseball game right there. He gives up a home run, that's fine. But we do the same (stuff) every day, day in and day out. That's the reason why we practice that."
Dunn also said that he regularly practices the play.
"Probably a million times. Every day," he said. "I'd like to know when the last time I dropped a ball like that. I don't know if I just took my concentration off for a split second and that was enough for me to drop it."
Two weeks ago, Espinosa moved to shortstop from second base when Ian Desmond when on the disabled list with an oblique strain. Espinosa has made five errors in 20 games at short after committing just four in 88 games at second base.
"I think the errors are pretty uncharacteristic of me. They're stupid errors," Espinosa said.
LaRoche homered twice off Marlins starter Mark Buehrle, giving LaRoche 23 this season.
Jordan Zimmermann started for Washington and allowed five runs -- four earned -- and seven hits in five innings.
The Marlins broke a 3-3 tie in the fifth. Bryan Petersen led off with a single off Zimmermann, moved to second on Scott Cousins' sacrifice, and scored when Espinosa fielded Reyes' infield single and threw it away. Reyes stole second and scored on Lee's double.
Buehrle allowed four runs and seven hits in six innings. He walked two and struck out two.
Miami scored an unearned run in the seventh when Reyes led off with a walk, stole second, moved to third on an error by Lombardozzi and scored on a squeeze by Donovan Solano.
Dunn hadn't given up a home run in his first 32 appearances of the season. ... The Marlins put 2B Emilio Bonifacio on the 15-day disabled list with a sprained left thumb. He reinjured the thumb on Friday. Miami purchased the contract of INF Nick Green from Triple-A New Orleans. ... Marlins INF Donnie Murphy missed his second game with a strained left hamstring. ... Miami OF Giancarlo Stanton, on the DL after right knee surgery, hit a home run in four at-bats in a rehab game with Class-A Jupiter. Guillen expects Stanton back when Miami plays in New York on Tuesday. ... Petersen had a season-high three hits. ... The Nationals sent C Sandy Leon to Triple-A Syracuse to make room for newly acquired C Kurt Suzuki from Oakland. Suzuki was hitless in three at-bats. ... Washington OF Michael Morse extended his hitting streak to 13 games. ... RHP Ricky Nolasco (8-10, 4.90) will pitch for the Marlins on Sunday against RHP Stephen Strasburg (11-5, 3.12).