MIAMI -- The rebuilding Atlanta Braves have Matt Kemp under contract for the next three seasons.

Even though that contract is huge -- $21.5 million per year -- the Braves don't seem to mind it because of the way he is hitting the ball.

That was on display again Thursday night as Kemp slugged two home runs and had three RBIs to lead Atlanta to its sixth straight victory, a 6-3 win over the Miami Marlins at Marlins Park.

Kemp, acquired from the San Diego Padres on July 30, has 10 multi-homer games in his career, including three this season.

"He's a really good player," Braves manager Brian Snitker said of Kemp, who has 33 homers and 104 RBIs this year. "He's a big, strong man. When he swings that bat, man, it goes."

Kemp is not Atlanta's only hot hitter.

Freddie Freeman, who drove in two runs, extended his hitting streak to 26 games. It's the longest active hitting streak in the majors and the longest by a Braves player since Dan Uggla had a run of 33 games in 2011.

The Braves (62-91) have the worst record in the National League but have been playing spoilers lately, sweeping three games at the New York Mets earlier this week and on Thursday knocking off the Marlins (76-77), who are barely alive in the pursuit of an NL wild-card playoff berth.

"You can get beat by anybody in this league," Marlins manager Don Mattingly said of the Braves, who are 10-6 against Miami this season. "Since they picked up Kemp, they have settled in -- he really changes their batting order.

"They've got a good ballclub. They are moving in the right direction."

Josh Collmenter (3-0) earned the win for the Braves, who are 18-12 since Aug. 21. Collmenter allowed five hits, two walks and two runs in seven solid innings.

Collmenter's overhand delivery kept the Marlins off balance.

"I was moving the ball in and out, changing speeds -- that's what I do," Collmenter said. "The second time through the lineup, I was able to use my curveball, getting ahead of hitters. I was throwing pitches that I wanted to throw. I was able to jam some guys and make them chase some pitches."

Jose Urena (4-8) took the loss, allowing five runs in three innings. In his past two starts, Urena has given up 12 runs in five innings.

Ender Inciarte started Urena's trouble, leading off the game with a triple to right-center and scoring on a groundout by Adonis Garcia.

On Inciarte's shot, Marlins center fielder Christian Yelich made a long run and got the tip of his glove on the ball as he crashed into the wall.

That triple was Inciarte's first play since Wednesday night in New York, where he raced back to a similar spot on the field -- right-center -- and took a home run away from Yoenis Cespdes that kept the Mets from a walk-off win. Atlanta won 4-3 on that catch.

Against Miami, Atlanta added to its lead with a four-run third. Freeman lined a two-run single just over the head of second baseman Dee Gordon, and Kemp followed with the first of his homers, a two-run shot to left.

Kemp homered to left again in the sixth, giving Atlanta a 6-1 lead.

Miami's J.T. Realmuto hit a solo homer in the seventh to cut Atlanta's lead to 6-2. It was Realmuto's 11th homer of the season, one more than he had as a rookie last year.

The Marlins made it 6-3 in the eighth on an RBI double by Martin Prado, who drove a two-out shot over Inciarte's head. However, that was as close at Miami got to the Braves.

Realmuto said he was disappointed in the loss, especially after Miami took two out of three games from the first-place Washington Nationals.

"We have to play more consistently," Realmuto said. "We have to get hot."

NOTES: Marlins RHP Jose Fernandez will make what could be his final start of the year Sunday against Atlanta. He would make another regular-season start only if the Marlins remain in the playoff race until the end, which appears unlikely. ... Marlins versatile RHP David Phelps could be the first major league pitcher since Bill Swift in 1990 to start at least five games, save at least four, pitch at least 80 innings and post an ERA under 2.50 in the same year. Phelps has done everything on the list, and his ERA is 2.40 so far. ... This is the first time since 2010 that the Marlins have three players with 20 or more homers -- RF Giancarlo Stanton, CF Christian Yelich and LF Marcell Ozuna. ... The Braves' bullpen is No. 1 in the NL in fewest homers allowed.