SAN FRANCISCO — The swing was so pure that it left a mark.

On Tony Vitello. From Drew Gilbert.

“It was such a pretty swing, Drew punched me,” the Giants manager said after his club rallied against the Marlins for a 6-3 win Sunday. “And [he] said, ‘That’s the swing!’”

While Casey Schmitt’s go-ahead home run in the seventh was a quality hack in its own right, the cut that caused a stir in the dugout came an inning earlier and got the comeback started.

The Giants hope it can be the start of something much bigger.

Almost a month in, Rafael Devers’ season-long slump has officially become a concern. Two soft outs on uncompetitive cuts in his first two at-bats Sunday did nothing to alleviate those worries.

But after Schmitt drew a walk to lead off the sixth, Devers changed course. He fell behind 1-2, and when reliever Calvin Faucher tried to sneak a fastball by him for strike three, Devers went with the low-and-outside offering and lined the ball into the gap in left-center field.

“Rafi’s got two strikes on him, and he’s just up there fighting — fighting the situation, rather than fighting himself,” Vitello said. “At times, at least that’s what it has appeared as.”

The ball left Devers’ bat at 108.2 mph and made it all the way to the wall. Schmitt scored from first to get the Giants on the board. In a way, it also got the middle of their lineup on the board. 

The RBI double delivered the first run driven in by any of their big three bats — Devers, Willy Adames or Matt Chapman — over the course of their six-game homestand.

“That’s what we’re here for: to drive in runs and be productive,” Chapman said. “But we are a team, and Casey’s hot right now. There’s other guys that are carrying our offense. It’s one of those things where we haven’t all really clicked yet, but I think that’ll happen.”

The Giants finished the set against the Marlins and Dodgers at 4-2 despite getting little to nothing from the middle of their order. The trio earning a combined $80 million this season went 8-for-61 with 23 strikeouts, seven walks and just three extra-base hits over the six games.

On the season, Devers’ .562 OPS ranks among the bottom 20 qualified hitters in MLB. Adames’ mark has sunk to .626 — in the bottom 40 — amid an 0-for-21 slump to end the homestand.

On Sunday, Vitello decided to give Adames his first day off this season. Together with Monday’s off day in Philadelphia, he’s hopeful that the extra rest will ignite Adames, who has been dealing with some general soreness while starting the first 27 games of the year.

“The hitting will come and go a little bit. But I do think it’s been affected a little bit by that,” Vitello said. “It’s a grind being out there every day.”

Vitello believes there’s a different solution to get Devers going.

“Right now the more at-bats we can get, the closer we get to even just maybe not the best but just the status quo version of what he’s capable of doing,” Vitello said before the game, adding that there was nothing bothering the first baseman physically. “I don’t think there’s a lack of confidence. I think there’s a large amount of frustration.”

Until then, the Giants will continue to make do with Schmitt’s clutch hitting — his second go-ahead home run in as many games — and ride the hot bat of Jung Hoo Lee, who reached four times in the win Sunday for his fourth multi-hit game of the homestand.

There’s been another, more subtle effect lately that’s aided the Giants’ offense: patience.

Their .250 batting average ranks in the top 10 in MLB, but their .295 on-base percentage is third from the bottom. The gap has begun to shrink as the Giants worked their way on base against Miami 11 times via the free pass, their most in any series this season.

Vitello, aware of the club’s dead-last 5.5% walk rate, said it has been an “emphasis” in hitters’ meetings. Perhaps it’s no coincidence that Schmitt’s tiebreaking homer was preceded by a walk in his previous trip to the plate.

“You don’t want to go up there and try to walk — that’s kind of a dangerous game,” said Chapman, who drew two in the win Sunday. “I would say it was more so [that] we’ve been making a lot of early, weak contact. So [instead], let’s really hunt for a pitch we want to drive and stay disciplined to that pitch. I think because of that the walks have been a byproduct.”

Consider it a step in the right direction for a club that seemed to take a few of them this week.

They took two of three from the mighty Dodgers, an accomplishment in its own right. When that momentum faded with losses in the series finale and the opener against the Marlins, they bounced back to win the last two against Miami.

The Giants had lost all but two of their first 15 contests in which they allowed their opponent to score first. They fell behind 1-0 early on Saturday and trailed 3-0 entering the sixth on Sunday.

Now, a team that hadn’t won consecutive series all season has now clinched three in a row.

“I think we’re growing up as a team,” Vitello said.