The Mets scored two runs in the fifth off rookie Mike Minor (3-0), but the 2-1 lead didn't last long. In the bottom half, the Braves knocked out Jonathon Niese (8-7), taking advantage of Castillo's blunder.
The second baseman let a likely double-play grounder slip between his legs, and the Braves made New York pay big time. Jason Heyward followed with a two-run double, Alex Gonzalez had an RBI single and Ross — Atlanta's backup catcher getting one of his occasional starts — cleared the bases by lining his second homer of the season into the left-field seats.
The slow-running Ross also had a triple.
Atlanta has bounced back from last week's four-game losing streak — its longest skid since April — with four straight wins. The Braves came into the night with a three-game lead over Philadelphia in the NL East. The Phillies had a late game against the Los Angeles Dodgers.
Nate McLouth, the Braves' former starting centerfielder just back from Triple-A, sparked the seven-run inning by getting plunked with a pitch as a pinch-hitter.
Omar Infante followed with a slow hopper up the middle — perfect for turning two — but Castillo let it skip right between his legs for an error that changed the whole complexion of the game.
Heyward lined a shot to left-center, bringing in two runners who shouldn't have been on base. Martin Prado followed with a single and Derrek Lee walked to load the bases.
Niese struck out Matt Diaz, but Alex Gonzalez singled to right to make it 4-2. Prado also tried to score, but former Brave Jeff Francoeur threw him out at the plate. Prado slid around catcher Henry Blanco, but too wide to touch the plate. Prado had no chance to get back before Blanco tagged him out.
Niese couldn't take advantage of the big defensive play. Ross ripped into a 2-2 pitch that turned a still-tight game into a rout.
The Mets took advantage of three walks by Minor to grab a short-lived lead. Francoeur and Blanco both had sacrifice flies.
After squandering scoring chances in the second (runner at third with one out) and the third (Ross' leadoff triple came to nothing), the Braves finally broke through in the fourth. Prado led off with a double and Lee brought him home by singling to left.
Coming off a 12-strikeout performance against the Chicago Cubs, which tied the Braves' rookie record, Minor struggled a bit in his fourth career start. He wasn't sharp on eight days rest, surrendering seven hits and three walks while striking out four in five innings.
Niese was lifted after Ross' grand slam, having surrendered 10 hits in 4 2-3 innings. Officially, three of Atlanta's run were earned, but it's likely the Mets starter would've given up nothing in the fifth if not for Castillo's costly error.
NOTES: It was a feast-or-famine night for Ross, who struck out in his other two at-bats. ... Mets 3B David Wright batted second for the first time since 2007 and just the 15th time in his career. He was 0-for-3 with a walk. ... Even with the Braves leading the NL East, the turnout at Turner Field was less than 20,000 for the second night in a row. The announced attendance was 18,430. ... New York OF Angel Pagan didn't play because of tendinitis in right wrist.