SAN DIEGO – The Giants’ infielders perched their toes on the lip of the grass as Cory Gearrin’s sinker arrived at 93 mph, and did exactly what it was designed to do.

It elicited such weak contact from Wil Myers that the Padres’ right-handed hitting All-Star hesitated to start toward first base. In the seventh-inning shadows, it was tough even for him to make out what had happened.

The ball skidded down the first base line and into right field. It drove home the tiebreaking run in the Giants’ 4-3 loss Sunday afternoon. It was an inside-out swing that left the Giants on the outside looking in.

No, the Giants did not blow another lead in the ninth inning, but it was just as catatonic when the bullpen let one slip in the fifth and fell behind in the seventh.

When the result is a fourth consecutive N.L. West title for the archrival Los Angeles Dodgers, and another hole in the grass on a three-team limp to a wild-card game, the play-by-play amounts to legal fine print.

“You knew it was coming,” said Giants manager Bruce Bochy, whose club actually was eliminated from the division race moments before making the 27th out, when former San Francisco prospect Charlie Culberson’s walk-off home run at Dodger Stadium set off a celebration there.

“So we’re battling for the wild card. It’s inevitable, the way the second half has gone,” said Bochy. “So that’s going to happen. You understand that. You always want to win your division, but our goal now is to win games and get there and have a shot at it.”

The Giants (82-74) fell out of a tie atop the N.L. wild card standings and now trail the streaking New York Mets by one game. The Giants remain a half-game ahead of the Cardinals, who lost to the Cubs, for the second wild-card spot.

They also might have lost their brightest spark, third baseman Eduardo Núñez, who left the game in the seventh inning with a right hamstring strain after stealing his 40th base of the season. Núñez already was playing through an oblique injury; he will get an MRI exam but kept alive hopes he could play Tuesday’s opener of a season-ending homestand.

“I wish I’d stayed at 39,” Núñez said, ruefully.

The Giants find themselves here, in a place where swim goggles and cigars have no utility, because of an inability to win series since the All-Star break. They have played 21 of them and captured just three.

They have not plunged in the standings so much as sunk into them as if into a tar pit, and as any wooly mammoth would tell you (if it could), trying harder to escape only compounds the problem.

They are 8-17 in one-run games since the All-Star break. They were 20-10 in such games prior to the break.

The Giants’ rotten run began here at Petco Park, when they arrived out of the All-Star break with baseball’s best record (and a 6 ½-game lead in the N.L. West) but were swept on their way to a six-game losing streak.

Since then, they haven’t lost more than four in a row. It’s been two out of three, then three out of four, two out of three, with the occasional four-game split to provide a flicker of hope.

They needed to do better than that in their final regular-season road series here.

Rookie Ty Blach made his first big league start, stepping in for the injured Johnny Cueto, and did well to hand over a 3-2 lead to the bullpen after three innings. But the Padres chopped across a run on George Kontos in the fifth, and Myers put them ahead in the seventh to split the four-game series.

Blach, a strike thrower who impressed in the Pacific Coast League, has a habit of skipping off the mound and jogging back to the dugout. He had to do quite a bit of scrambling as well. He pitched a scoreless first inning despite giving up a double and walking three, escaping in part because of a double-play grounder sprinkled into the mix.

Blach showed moxie in the second inning, persevering through a 14-pitch battle with Myers that ended with a strikeout on a 93 mph challenge fastball.

That little victory only came after the Padres had scored a run on a single, a sacrifice and a two-out hit from recent call-up Manuel Margot. They got another in the third when Adam Rosales hit a 325-foot cheapie to the opposite field that barely snuck over the fence in the right field corner.

“I was just a little quick with everything,” said Blach, who also committed a balk.

“It didn’t seem like him,” catcher Trevor Brown said. “He’s really good at getting over his front side and finishing his changeup when he gets his hand out in front.”

The Giants went ahead with a three-run third inning that included a clutch hit from Buster Posey and a very big mistake.

Brown hit a leadoff single, and Blach’s sacrifice attempt died in front of the plate. Padres catcher Austin Hedges dropped the ball and bumped into Blach as he lunged a second time for it. Then his throw to second base sailed into right field for an error as Blach ran safely to first base. The Padres argued for an interference call that did not come.

Núñez singled to load the bases, Kelby Tomlinson hit an RBI ground out and Posey lined a two-run single to right field off left-hander Clayton Richard.

But the Giants could not add to their lead, and bullpen could not complete the gauntlet-running task of recording 18 outs while protecting a one-run margin.

Another of those poison-dipped leadoff walks didn’t help. Myers drew one and stole second base off Kontos in the fifth, then scored the tying run on Yangervis Solarte’s single.

After an inning of impressive work from Steven Okert, Gearrin gave up a one-out triple to Margot. Then he made a pitch to Myers that resulted in a ground ball that hit the dirt in front of the plate and scooted through the shadows down the first base line.

“As a right-handed hitter against a (sinker-slider) pitcher like that, to hit a ball down the line is so hard,” Brown said. “It’s not something you try to do. You almost shake your head in disbelief. It’s like, `How did that go down the line?’”

Posey, playing first base well off the line, had no chance. Regardless, he stayed rooted as if he never saw it.

“That’s what we wanted there, a weak ground ball,” Gearrin said. “I liked the way Brownie called that at-bat. Not much you can do. Sometimes you make a pitch, and it finds a hole. … I came back in (the clubhouse), and Dave Righetti told me, “(Myers) didn’t see it. He didn’t even know where it was at.’”

The Giants never could have seen this: losing a division they led by eight games in late June.

There is still time for them to come back and be a playoff team. But they likely must win their remaining two series, at minimum — and after doing that successfully three times out of 21, it’s more direct to believe that the die has been cast than that they’re due.

They aren’t much for comebacks, these Giants. They fell to 0-61 when trailing after eight innings.