Atlanta took two of three games from the first-place Marlins and trail them by only percentage points. The Braves haven't lost a series to their division rivals since 2017, and are 31-10 against Miami over the past three seasons.
"Our mindset is the same with everybody," Markakis said. "It doesn't matter who we're playing. But division games are extremely important."
Markakis, who opted out this year because of the coronavirus and then changed his mind five games into the season, had two hits and improved his average to .323.
"Just having him here makes me feel better and more at ease," Braves manager Brian Snitker said. "He'll do anything. He's just good to have around. He's kind of like my security blanket."
Markakis' RBI single in the sixth off Nick Vincent (1-1) gave Atlanta a 1-0 lead. The Braves added three runs in the seventh after their first two batters were retired, and Markakis' two-run double made it 4-0.
"That's what I'm here for -- I'm here to help out and win as many games as I can," Markakis said. "My team got me in position where I could drive in some runs today, and it worked out."
Dansby Swanson had two hits and scored twice for the Braves, who won despite striking out 16 times.
Atlanta's Robbie Erlin, making his first start of the year, allowed only one baserunner in four innings.
"He's a strike thrower who can change speeds," Snitker said. "He's got a little funky delivery. His ability to throw the ball over the plate is so refreshing here."
Darren O'Day (2-0) pitched 1 1/3 innings to highlight the latest strong effort by the Braves' relief corps.
"The bullpen has been great," Erlin said. "There's so much experience. Every time the phone rings, everybody is ready to go."
Two of Miami's three baserunners were erased on double plays.
Seeking more punch from a Braves lineup without the injured Ronald Acuna Jr. and Ozzie Albies, Snitker moved Freddie Freeman up to the No. 2 spot. It was the first time Freeman hit there since 2011, and he went 1 for 4.
Snitker said he likes the lineup because, with the designated hitter, the No. 2 spot doesn't come two batters after the pitcher.
"It's something I may explore more," Snitker said. "Freddie came up in some big spots today. With the DH thing, going forward it may not be a bad thing."
But the Braves mustered only three hits against Miami starter Elieser Hernandez, who struck out nine in five innings.
"Anytime you get good pitching you'd like to be able to put some runs on the board for him," Marlins manager Don Mattingly said.
Mattingly was ejected in the fifth inning for arguing about umpire James Hoye's strike zone.
Eighteen players who went on the injured list following the Marlins' coronavirus outbreak have reported to the team's spring training site in Jupiter, Florida, to begin workouts.
The group includes starting pitchers Sandy Alcantara and Jose Urena, catcher Jorge Alfaro and shortstop Miguel Rojas. It's unlikely any of the players will be activated before the next homestand, which starts Aug. 28.
As part of MLB's celebration of the Negro Leagues, the Marlins wore uniforms honoring the Miami Giants, a 1930s semipro team.
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Dodgers blow most of 13-run lead, still outlast Angels 14-11
— Mookie Betts drove in a season-high four runs, and the Los Angeles Dodgers blew most of a 13-run lead before holding on for a 14-11 victory over the Los Angeles Angels on Saturday night, snapping their four-game losing streak in hair-raising fashion.
Dodgers break game open with 8-run 4th
The Dodgers tag the Angels for eight runs in the fourth inning.
Rojas pummels 433-foot HR to cap off Angels' 7-run inning
Jose Rojas sends the ball into the right field stands to cut the Dodgers' lead to 14-11 in the seventh inning.
Adrianza, Braves rally for 8-7 win over Phillies in 12th
— Ehire Adrianza capped a night full of comebacks for Atlanta with a game-ending RBI single in the 12th inning, helping the Braves stun the Philadelphia Phillies for a chaotic 8-7 victory Saturday.
Braves stun Phillies with dramatic comeback in the 12th
William Contreras hits a bases-clearing double to tie the game, and then Ehire Adrianza wins it with a walk-off hit for the Braves.
Sandoval's clutch HR ties game with Braves down to final strike
Pablo Sandoval keeps the Braves' chances alive with a game-tying home run in the bottom of the ninth.