Gee stopped the longest losing streak of his career at five games, outpitching Alex Wood in the opener of a three-game series. Lagares, one of the best defensive outfielders in baseball, scurried from gap to gap and finished with seven putouts.
''That's Lagares, man,'' Gee said. ''We expect that from him now. Unbelievable center fielder. Makes great plays. ... I'd be hard-pressed to find anybody better. He's unbelievable. He's fun to watch.''
One of Lagares' grabs was spectacular - he robbed Wood of a base hit with a diving, tumbling grab in shallow center to end the third inning. Lagares also began the game by running a long way to track down consecutive fly balls, and he made all three putouts in the sixth.
''I'll tell you what: Everybody's impressed - I'm not. I've been playing with him since `09. I know what he can do,'' New York infielder Wilmer Flores said. ''Any pitcher would want him in center field.''
''I think I liked both,'' Lagares said with a grin.
Right in the thick of a crowded NL wild-card race, the Braves have totaled only five runs while dropping three straight after a 7-1 stretch.
Streaking slugger Justin Upton went 3 for 3 with an RBI double and a walk.
''He's really swinging the bat really well. We've got to get some people on in front of him,'' manager Fredi Gonzalez said.
Backed by three double plays, a clean-shaven Gee (5-6) gave up two runs and six hits in 6 2-3 innings. He entered 0-5 with a 5.71 ERA in seven starts since beating the Braves 4-1 on July 9 in his first outing after nearly two months on the disabled list with a strained right lat.
New York turned four double plays in all.
''It just killed us, really,'' Gonzalez said.
Mejia leaped off the mound with both arms raised after throwing a called third strike past Evan Gattis to end it.
Wood (9-10) retired his final 12 batters after Lagares' homer in the fourth. The left-hander struck out six and walked one in seven innings. He yielded two earned runs or fewer in each of his previous five starts.
Travis d'Arnaud doubled to open the bottom half and Lagares drove Wood's full-count changeup to left field for his fourth home run - his second in three games after going more than three months without one.
''It was just a really bad pitch to that guy,'' Wood said.
Braves: RHP Cory Gearrin is ready to begin a throwing program in his rehabilitation from Tommy John surgery in April.
Mets: Wright left Sunday's 11-3 win at Dodger Stadium with a muscle spasm on the right side of his neck that he said is getting better. Murphy, who leads the NL in hits, was removed late in that game due to tightness in his right calf and said he's day to day. He expected to be examined by a doctor Tuesday evening. Mets manager Terry Collins said he's not sure how long either player will be out. ... RHP Daisuke Matsuzaka (elbow inflammation) is scheduled to make another rehab start Thursday for Class A Brooklyn, Collins said.
Eric Campbell replaced Wright at third base and batted third. Flores shifted over from shortstop to Murphy's spot at second. Campbell and Flores combined on a pair of 5-4-3 double plays, including one in the ninth.
New York has totaled 12 homers while going deep in seven consecutive games, its longest streak since a seven-game power surge in September 2012.
All-Star RHP Julio Teheran (12-9, 2.96 ERA) pitches Wednesday night for Atlanta against RHP Zack Wheeler (9-8, 3.48 ERA), who has won six straight decisions. Wheeler is 3-1 with a 3.50 ERA in six career starts against the Braves, his hometown team.