SAN DIEGO — The thing about Madison Bumgarner leading the team in home runs is that Madison Bumgarner will let you know that he leads the team in home runs.

“That was my main objective today,” Brandon Belt said. “Passing him.”

Belt did, hitting his first career grand slam and a solo shot two innings later. He’s tied for the major league lead with three homers, and when Bumgarner walked up in the clubhouse late Friday night, two overflowing bags of definitely-not-store-bought jerky in his hands, Belt pointed out that the tables had turned.

“That’s okay,” Bumgarner said slowly. “I play tomorrow.”

The moment was a reminder of how much has gone right for the Giants this week. Bumgarner was outstanding on Sunday and Belt looks poised for a career year. Others up and down the roster have gotten off to hot starts or contributed with big moments.

But the only number that matters thus far is eight. It’s the number of leads the pitching staff has blown, and it’s led to a 1-4 start. On Friday, Belt’s slam got Matt Cain off the hook. George Kontos, who had thrown better than any reliever over the past two weeks, gave it right back. The Giants fell 7-6 to the rebuilding Padres.

“We were going to have a 1-4 stretch at some point,” Belt said. “It just happened to happen early.”

There’s much more than a grain of truth in that. Every team has a run like this, but this team — coming off a second half and postseason of blown leads — would have preferred any other start to the season. It’s not so much that the Giants are blowing leads. It’s that it seems contagious. Kontos entered having struck out nine of the previous 10 batters he had faced. He got through the heart of a dangerous Diamondbacks lineup on Tuesday, earning a look in the seventh inning Friday. It went off the rails quickly.

Travis Jankowski walked and Wil Myers hit a single up the middle. Yangervis Solarte got a cutter that wasn’t far enough in on his hands, and he blasted it to right-center. The Padres had the lead, and they would tack on an insurance run that became important when Belt blasted his third homer of the year to dead center.

“I felt fine,” Kontos said. “I just didn’t do a good job of executing pitches.”

It seems there’s no right answer for Bruce Bochy at the moment, but he hid any displeasure, saying this in a bullpen in transition, and roles will become clear.

“It’s early. It’s the first week,” Bochy said. “We’ll get it figured out and they’ll settle into roles they’re comfortable in. This is a process. Ideally, you have it set up. We like to think we do. But this was a hiccup. George left a lot of pitches up and they took advantage.”

Cain did the same, giving up four runs in 4 1/3, including two homers to young center fielder Manny Margo. Again, execution mistakes, the theme of the young season.

“I wasn’t as sharp as I need to be,” Cain said.

Cain fell behind early to young right-hander Luis Perdomo, who fired 96 mph sinkers at the knees for five innings. In the sixth, he loaded the bases ahead of Belt. A slider hung at the knees and Belt crushed it.

“My goal right now is not to guess,” Belt said. “I just want to see the ball. I feel if I can do that, my hands will go. That’s what I did there.”

It was an impressive swing, one that brought Bumgarner sauntering over an hour after the final out. Given the early schedule, the ace should have been preparing to put an exclamation point on a hot start. Instead, they're hoping he can salvage the week.