Carlos Carrasco makes another strong start as Mets beat Braves to complete double-header sweep at Citi Field

Pete Alonso’s RBI single in the second helps the Mets beat the Braves in Game 1 of a double-header on Tuesday. (Frank Franklin II/AP)

If you’re going to play two, might as well win them both.

The Mets triumphed over Atlanta — likely their stiffest test in the division this year — in both games of Tuesday’s doubleheader. With the pair of wins (the first by a score of 5-4, the second a more comfortable 3-0), the Mets are now 18-8 and leading the division handily.

“It was a good day for us,” Buck Showalter said afterward. “We’ve got another challenge tomorrow. We’re playing three games in less than 24 hours.”

In the first game, the Mets dodged a bullet in the shape of a big, fat E1 on Tuesday afternoon, as what could have been a crucial fielding blunder by pitcher David Peterson ended up as nothing more than a footnote.

In that gray afternoon game, the Mets’ 5-1 lead quickly became 5-4 when Matt Olson followed Peterson’s error with a three-run crack into the Braves’ bullpen. Peterson, the obvious odd man out whenever Jacob deGrom returns from his scapula injury, was solid but unspectacular yet again.

His final line (five innings, four hits, four runs, six strikeouts) would have been much prettier if he was able to turn Ozzie Albies’ comebacker into an inning-ending double play. Instead, Albies became a base runner ahead of Olson’s home run, and one of the runs that turned a leisurely walk in the park into something much more stressful.

That’s why it pays to have talent in the batter’s box.

The Mets got all of their RBI in the first game from Francisco Lindor and Pete Alonso — their incumbent superstars — as well as Mark Canha and Eduardo Escobar, two of the transformational acquisitions from the offseason. Not to be outdone, Travis Jankowski (who was signed to a minor league deal three weeks before the season started) added two hits and scored three crucial runs while holding down the leadoff spot for the first time as a Met.

“He’s as excited as a guy going to his first game in Little League, playing today and leading off,” Showalter said of Jankowski, a guy who readily admitted after the game that he’s not the type of player that causes fans to buy his jersey. “Guys like him and [Luis] Guillorme bring it in situations like this. Trav’s been a pro. That’s why we wanted to keep him. He brings some tools that we need. He’s a great piece for us.”

The second game hummed along at a similarly brisk pace, a likely combination of long-day fatigue and very astute starting pitching. Both starters finished seven innings, but the Mets’ Carlos Carrasco went a season-high eight, gave up zero runs, and emerged victorious over Atlanta’s Kyle Wright.

“I wanted to throw as many innings as I could to save the bullpen, and everything went the way I wanted it to,” Carrasco said.

On Tuesday night, Carrasco allowed a leadoff double to Ronald Acuña Jr. to begin the game, then allowed just five more hits for the night.

The Mets’ offense in the second game was limited to the first and sixth innings. Dom Smith sliced a two-run double into the left field corner to greet Wright, and Alonso piled on with a solo shot the other way to put the Braves’ phenom in more of a hole.

Smith’s at-bat in the sixth inning made for some more intrigue when Max Scherzer was ejected from the dugout after arguing the third strike call. Scherzer, who has only ever been ejected from games he did not pitch in, told reporters afterward that his comments to the umpire included profanity and he was simply saying what Smith was unable to.

Alonso’s home run was not only great insurance, but also made sure that the Braves’ unwavering defense wouldn’t spoil the occasion. The first game saw Olson sprawl into the grass in foul territory to make a diving catch on Tomas Nido’s bunt attempt. Later in the same game, Albies matched him with a diving snag of his own, snaring a hard-hit ball in shallow right field and firing to first to rob Lindor of a hit.

The biggest defensive play of the day, albeit a fairly easy one, came from a Mets outfielder, though. With the Mets clinging to their 5-4 lead in the seventh inning of the first game, Olson came up again, this time to face reliever Drew Smith. Olson ran the count full before taking the sixth pitch for a ball, sending up the equally powerful Austin Riley.

Riley came up hacking, fouling off two pitches. On a 2-2 count, the crack of his bat rang through a tense Citi Field, sending hearts into throats and outfielders to the warning track. But Starling Marte had just enough room — right where the right-center field fence juts in from the 380-foot mark — to make the catch.

Smith also came back for the eighth and set the Braves down in order. The unheralded pitcher has now begun his season with 10 straight scoreless appearances, giving him a 0.00 ERA in 11.1 innings. Smith, like his namesake on the offensive side who had a timely 4-for-4 game on Sunday, simply played too well for the Mets to send him down during their recent roster cuts.

“I can’t think too much about what’s happened in the past,” Smith said after logging two more clean innings. “You just gotta reset every time. It’s a good start, but it’s barely May. It’s a long season.”

The Edwin Diaz trumpets came in the ninth, and with Smith having already gotten through the thick of Atlanta’s lineup, the voltaic closer held on for his fifth save of the Mets’ season.

After Carrasco’s eight-inning mastery of the Braves’ lineup in game two, Diaz’s services were unneeded, as Seth Lugo shut things down for a speedy finale.