MIAMI — In a series in which hardly anything had gone right, the Giants still had to feel good about their chances Sunday with their ace, Logan Webb, on the mound.

The odds were even more in their favor given the Marlins countered with Ryan Gusto, a 27-year-old from Santa Rosa with a 5.85 ERA in 32 career big-league games.

Webb held up his end of the bargain.

But the Giants’ hitters showed no gusto against Gusto.

They struck out six times in 4 ⅓ innings against the Marlins’ meager starter, cracked him for just one run and fared no better once Miami went to the bullpen in a 2-1 loss.

“Obviously you want more runs and you want to win,” manager Tony Vitello said. “But if you pull the two [or] three innings of bad baseball yesterday, the guys played well. We just unfortunately don’t have a lot to show for it.”

The defeat completed a sweep at the hands of the Marlins and sent San Francisco 15 games below .500, matching their low point of the season previously set last weekend, when they fell to 28-43. They responded by reeling off three consecutive wins against the Cubs and Braves.

But, just like that, another three losses followed.

“It’s frustrating,” said third baseman Matt Chapman, who went 0-for-19 with eight strikeouts on the road trip. “Because it seems as soon as we have some momentum, it’s a couple steps forward and a couple steps back.”

No fault of Webb, who only made a couple of mistakes in an otherwise flawless outing. Webb limited Miami to two runs on five hits, completing eight innings for his third consecutive start.

There were probably only two at-bats he wished he could have back, and they both came against Kyle Stowers. The Marlins’ cleanup hitter punished a first-pitch sinker that didn’t quite get low enough for a home run that put Miami ahead 1-0 in the second inning and, in his next time up, worked a two-out walk that allowed Otto Lopez to double him in to make it 2-1.

“Bad pitch to Stowers,” Webb said. “And a two-out walk just can’t happen.”

The Giants advanced just two runners into scoring position, both in the third inning, when Luis Arraez sliced a two-out double into the left field corner and Casey Schmitt singled him home.

Bryce Eldridge, who reached on a walk, made it to third but was stranded there.

From the fourth inning on, the Giants mustered only four baserunners and failed to advance any of them beyond first base. With closer Pete Fairbanks unavailable having saved the last two games, the Marlins brought in Lake Bachar, who faced zero resistance in the ninth.

“Their bullpen guys did a good job all three days,” Vitello said. “You use that many guys, you’d like to think you’ve got a window that opens up when a guy’s not on that guy or doesn’t execute, but the way they lined them up was pretty good. We did have decent matchups on paper, but the bottom line is those guys got the job done for them.”

The most resistance shown by any of the Giants in the ninth, in fact, was friendly fire from Rafael Devers when Jonah Cox was called on to pinch-run after he drew a leadoff walk.

Devers unsuccessfully appeared to try to wave off Cox and stormed back to the dugout in a huff, twisting his body to avoid a pat on the back from Jayce Tingler and beelining to the clubhouse.

“You know how competitive he is,” Vitello said, downplaying the incident. “He wanted to stay in the game.”

Webb allowed more than one run for the first time in five starts since returning from a bout of bursitis in his right knee. Still, only the Brewers’ Jacob Misiorowski, the MLB ERA leader, has posted a lower ERA than Webb’s 1.02 mark since he made his return May 29.

“The first outing [back from the IL] against the Rockies was good; it wasn’t phenomenal by any stretch of the imagination,” Vitello said. “But since then, he’s climbed every time he’s gone out there.”

Vitello moved Schmitt down in the order in the last game of their homestand, and he responded with his first of five straight multi-hit games from the bottom half.

That got him back in the No. 3 hole Sunday, and all Schmitt did was continue to hit.

He raked two more singles, including one that produced the Giants’ lone run for his team-leading 42nd RBI, in his sixth consecutive multi-hit effort.

It’s only the sixth time since 2000 that a Giants player has recorded multiple hits in at least six straight games, last done when Marco Scutaro strung together seven in a row in 2013.

“I think he’s back into the rhythm that he was [in],” Vitello said. “There was a little bit of a lull there. It was a matter of time before he got back going.”

Chapman, on the other hand, couldn’t buy a hit on this road trip.

Just as the third baseman seemed to have put it all together at the plate this month, Chapman has been out of whack seemingly every time he stepped to the plate the past five games.

Chapman looked increasingly lost as the trip went on, striking out eight times over the final four contests — caught looking in four of those instances.

“I got pitched well on this road trip,” Chapman said. “I still hit some balls hard but right at guys. That’s the ebbs and flows of the game. Just unfortunate when we’re not winning baseball games. It sucks.”

In his prior 26 games, dating back to May 17, Chapman was batting .344 with a 1.079 OPS, recording six of his seven home runs and 24 of his 41 RBIs over the stretch to raise his OPS to .762, the highest it had been since the second week of the season.

His latest cold snap sent his OPS back down to .716.

The Giants fly back to San Francisco, where they begin a six-game homestand Tuesday against the Athletics. It remains to be seen how warm of a welcome home they’ll receive with some fans organizing protests against the players who objected to the team’s LGBTQ Pride Night.

Tyler Mahle will make his first start since May 26 on Wednesday in his return from a hamstring strain, following Robbie Ray — who opens the series Tuesday.