ATLANTA — Hall of Famer Reggie Jackson had a saying that any struggling big-leaguer can understand.

“If you have a bat in your hands,’’ Jackson said, “you can change the story.’’

Anthony Volpe, for one night at least, changed his story. And Trent Grisham added to his, hitting a tiebreaking two-out grand slam in the top of the ninth inning to give the Yankees a stirring 12-9 comeback win over Atlanta on Saturday night in front of 42,530 at Truist Park. They had trailed 5-0, 7-2 and 8-6 and scored in the final five innings.

“I think it just shows and encourages everybody that we’re in every game,” said Grisham, who has 17 homers, 13 of which have either tied the score or given the Yankees the lead. “I think it’s big for us going forward, knowing no matter what game we get in down the stretch that we’re in it. So every starter that gives up a couple runs, every bullpen guy that comes in knows that this offense is going to keep going and not quit.”

But it was the horribly slumping Volpe, in a 12-for-99 skid entering the night, who earned game MVP honors. He hit two home runs — the latter a 411-foot solo shot off lefthander Dylan Lee with one out in the eighth inning that tied it at 8-8 — and drove in four runs.

As the Yankees (54-44), who remained three games behind AL East-leading Toronto, slumped toward the end of the first half, Volpe became the focus of their offensive struggles. He came into Friday hitting .212 with a miserable .287 on-base percentage.

“I have my standards for myself, and any of the stuff on the outside doesn’t come close to the standard I hold myself to,” he said of the criticism. “Even nights like tonight, on a good night, you still know you have to go right back to work. Good or bad, nothing changes from that side.”

Luke Weaver set up Volpe’s eighth-inning heroics by escaping a bases-loaded, one-out jam left for him by an erratic Jonathan Loaisiga in the bottom of the seventh. That kept it a one-run game.

“Well, vacation is over, indeed,” the typically witty Weaver said of his thoughts coming into the bases-loaded jam. “Just a lot of adrenaline going. A big moment.”

Volpe hit a 420-foot two-run shot in the fifth to cut the Yankees’ deficit to 5-2. It was the first career multi-homer game for the third-year shortstop. He also drove in a run with a sacrifice fly in a four-run sixth as the Yankees pulled within 7-6.

Paul Goldschmidt doubled to center off Raisel Iglesias to begin the ninth — Michael Harris II had a play on the ball at the wall, but it came out of his glove — and Cody Bellinger flied out. Atlanta (43-54) intentionally walked Aaron Judge and Giancarlo Stanton worked a walk to load the bases.

Jazz Chisholm Jr. hit a laser right at third baseman Nacho Alvarez Jr. for the second out. Hardly discouraged, Grisham hammered Iglesias’ 1-and-1 slider 406 feet to right-center for a grand slam and a 12-8 lead.

“He’s been huge for us,” Aaron Boone said. “You trust him in big spots to have a real quality at-bat regardless of result.”

The comeback pushed Will Warren’s subpar outing, one in which he allowed five runs, five hits and three walks in 3 2⁄3 innings, into the background.

Warren, who had allowed a solo homer by Harris in the third, retired the first two batters in the fourth but wound up throwing 41 pitches in the inning. Drake Baldwin doubled and Sean Murphy walked to set up Ozzie Albies’ second three-run homer in two games as Atlanta went ahead 4-0.

It became 5-0 later in the inning. No. 9 hitter Nick Allen hit a grounder toward the hole at second, where Goldschmidt made the stop. But Warren was slow getting over to cover first and compounded that by realizing too late that Alvarez was getting waved around third by coach Freddi Gonzalez.

“I felt like I was cruising,” Warren said. “I think the walk to Murphy was really [the difference]. Pulled some sliders out of the zone, good takes on his part after chasing the first one, and then Albies runs into a heater that’s not supposed to be in, it’s supposed to be away.”

After Albies’ two-out, two-run single in the fifth made it 7-2 and gave him nine RBIs in two games, the Yankees took advantage of the gasoline two Atlanta relievers threw on the proceedings and a critical error to score four times to make it 7-6.

Bellinger’s 17th homer, a solo shot off Pierce Johnson leading off the seventh, brought the Yankees within 8-7.

When Chisholm, who drove in the first of the sixth-inning runs with a single, reached third base, he could be seen shouting toward the Atlanta dugout. Coach Eddie Perez appeared to be yelling at Chisholm about stealing signs while on base and pointed at his head multiple times, as if to suggest that’s where Chisholm might get a pitch his next time up (that was the speculation among the Yankees).

Chisholm was not in the clubhouse when the media was allowed in and Boone kept his comments on the matter brief. “Not entirely sure,’’ he said, “but I know they were saying some things that will probably be looked at, and should be.”