Hefner (4-8) compiled a 1.76 ERA in his final eight starts before the All-Star break, the best mark in the majors during that span. But he was tagged for a career-worst eight runs and 10 hits in two-plus innings last Friday against Philadelphia, a personal nemesis throughout his two-year career.
The right-hander wasn't much better against Atlanta, allowing a career-high three homers in 4 1-3 innings. All of them were no-doubters, too.
"Obviously coming out of the break, he's not the same guy he was going in," Mets manager Terry Collins said.
Gattis hit a solo shot into the second deck in left field in the second inning, his first home run since June 10 in San Diego. Despite spending 24 games on the disabled list with a strained muscle on his right side, he leads major league rookies — by a wide margin — with 15 homers and 39 RBIs.
McCann reached on an error to start the fifth when Murphy, playing deep on the outfield grass, bobbled an attempted backhand. Gattis singled and Uggla drove the next pitch to left for his 20th home run.
Chris Johnson singled and, one out later, Simmons teed off on a 2-2 breaking ball to make it 6-0.
Simmons also hit a leadoff homer Tuesday night for Atlanta's only run.
"Obviously, it's frustrating. The team is playing well, we're playing good defense and we're scoring runs and I'm not holding up my end of the deal," Hefner said. "To have my performance tonight is unacceptable."
NOTES: Braves RHP Brandon Beachy, recovering from Tommy John surgery in June 2012, was set to make another rehab start Wednesday night for Triple-A Gwinnett. With Hudson hurt and LHP Paul Maholm (bruised left wrist) about to go on the 15-day disabled list Thursday, Beachy could be back in the rotation soon. ... Rookie left-hander Alex Wood will be called up to start the series finale Thursday in Maholm's place. The 22-year-old Wood (0-2, 2.45 ERA) has made 16 major league appearances but only one start, when he lasted three innings in a June 18 loss to the Mets. He has since been stretched out in the minors, and Gonzalez said Wood could be pushed to about 90 pitches Thursday. ... Gonzalez said Maholm will make a minor league rehab start before returning from the DL. ... RHP Zack Wheeler (3-1, 3.58) pitches for New York on Thursday. The prized rookie threw six shutout innings at Atlanta to win his big league debut June 18.