SAN FRANCISCO -- Three days ago in San Diego, Brandon Belt came off the bench and drilled his first home run since June 15. It was an encouraging sign for the 34-year-old first baseman, who had been mired in a 7-for-47 (.149) slump in 19 games since returning from the injured list.

“Maybe this is the home run that sets him on track,” manager Gabe Kapler said afterward.

Kapler’s words are proving prescient.

With a three-hit night on Monday, Belt is now 6-for-7 with a home run and two doubles over his last three games, though his surge wasn’t enough to keep the Giants from falling, 4-3, to the D-backs at Oracle Park.

After exploding for 12 runs on 17 hits in a blowout win over the Padres on Sunday, the Giants fell flat in the first game of their final homestand before the All-Star break, mustering only five hits against Arizona right-hander Merrill Kelly.

Kelly took a 4-1 lead into the eighth, though he was removed after issuing a leadoff walk to LaMonte Wade Jr., setting the stage for a late rally against All-Star reliever Joe Mantiply. San Francisco caught a couple of breaks, as Darin Ruf beat out a tapper to the left side for an infield single, and Wilmer Flores followed with a grounder that hit the bag and bounced over the head of third baseman Josh Rojas for an RBI double, cutting the D-backs’ lead to 4-2.

Despite Belt’s productive night, the Giants decided to have Austin Slater pinch-hit for him against Mantiply, a maneuver that paid off when Slater delivered an RBI groundout that pulled the Giants within one. Luis González then drew a walk -- the first free pass issued by Mantiply since his first outing of the season on April 7 -- prompting D-backs manager Torey Lovullo to summon right-hander Noé Ramirez to face David Villar.

Villar worked another walk to load the bases with one out, but Ramirez managed to induce an inning-ending 3-6-1 double play, with shortstop Geraldo Perdomo’s throw to first base narrowly beating out Brandon Crawford. The Giants challenged the close play, but the ruling was upheld following a replay review.

“I think with the way it lined up, it felt like we were about to break the game open there,” Kapler said. “Things seemed to break our way up until that point, and then they didn’t. It’s the luck of the draw in baseball sometimes.”

The loss -- the Giants’ ninth in their last 12 games and their fifth straight at home -- snapped the club’s 12-game winning streak against the D-backs at Oracle Park that had dated to Sept. 5, 2020. San Francisco has dropped three of its four meetings against Arizona this year, absorbing more losses over the past week than it did in all of 2021, when it went 17-2 against the National League West foe.

“We’re just trying to string wins together at this point,” said right-hander Alex Cobb, who was charged with the loss after giving up three runs on six hits over six innings. “It’s frustrating to lose a game the way we did. It felt like we had all the momentum in the world coming out of San Diego.”

Belt, who is still dealing with a bit of knee tenderness that flared up over the weekend, started at designated hitter on Monday and began his night by reaching on a popup that eluded four D-backs and fell for a leadoff single in the second. He added another single in the fourth before just missing a home run in his final at-bat in the sixth, when he crushed a 398-foot double off the right-field wall. Belt could only shake his head as he reached second base, and for good reason -- the drive would have been a home run in 29 other ballparks, according to Statcast.

Still, Monday’s results could be a sign of better nights to come for Belt, who led the Giants with a career-high 29 home runs last year but has been slowed by injuries this season.

“He’s looking a little more locked in,” Kapler said. “Obviously, we’re still thinking about his knee and getting him right. But he’s feeling good in the batter’s box. He sort of predicted that this was coming. No surprise. He knows when he’s starting to heat up, and it seemed like he was trending in the right direction. I’m looking forward to seeing him stay consistent with his swing because he can really carry us when he does.”