SAN FRANCISCO – All season long, Giants veteran Alex Cobb has pitched better than his final lines have indicated. On Friday night, the quality of his stuff finally began to match up with his results. 

Cobb allowed only three hits over five shutout innings in one of his strongest starts of the year, but he was let down by his offense in a 1-0 series-opening loss to the White Sox at Oracle Park.

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The Giants couldn’t capitalize on a bases-loaded scoring opportunity against Chicago right-hander Lance Lynn in the first inning and scarcely threatened afterward, finishing the night with only three hits en route to suffering their eighth loss in their last 11 games.

The White Sox finally broke the stalemate in the top of the ninth, when Gavin Sheets reached on an error by closer Camilo Doval, who was late covering first base and missed a feed from Brandon Belt. The miscue proved costly, as pinch-runner Adam Haseley came around to score the lone run of the game on Leury García’s go-ahead single to right field.

“From a team standpoint, we threw eight shutout innings, and one mishap in the ninth kind of cost us,” Cobb said. “But those games happen. … There’s going to be games where offense picks us up. It’s just baseball. You hope that it all clicks each night, but you go through stretches like this where if the pitching is not there, the next night the hitting might not be there.”

Cobb entered Friday with a 5.48 ERA through his first 10 starts, though several advanced metrics suggested the mark was misleading. According to Statcast, Cobb’s expected ERA was 2.34, tied for the best in baseball with Rays left-hander Shane McClanahan.

The wide gap between his ERA and expected ERA – the largest in the Majors -- can partly be explained by the Giants’ struggles to back him up defensively. Cobb has posted a career-high 62.3 percent ground ball rate this year, but San Francisco’s defense has recorded -7 outs above average with the 34-year-old right-hander on the mound, tied for the fourth-worst in baseball.

“Cobber’s stuff has been as good as anybody that we’ve had on our staff,” manager Gabe Kapler said. “I think it’s been some of the best stuff that he’s had in his career. Health has been a concern. And we haven’t been the best at converting outs for Alex. I don’t think that’s any secret.”

The Giants managed to play crisper defense behind Cobb on Friday, with center fielder Mike Yastrzemski adding to his expanding highlight reel with a spectacular running catch to rob Yoán Moncada of extra bases in the fifth. Moncada’s drive to left-center field came off his bat at 101.9 mph and had an expected batting average of .820, but Yastrzemski managed to run it down at the warning track, prompting Cobb to thrust his hands in the air in a show of appreciation.

“What Yaz did was really game-changing, even though we ended up losing,” Cobb said. “That inning could have really spiraled out of control, with the next couple of guys getting hits, too. I can’t even express the value that has and the motivation it gives you on the mound when you’re able to get some breaks and guys pick you up.”

Cobb was making only his third start since returning from the injured list and had begun to give up some hard contact in the fifth, so the Giants decided to pull him even though he needed only 67 pitches to complete his first scoreless outing of the year.

Still, his strong start was an encouraging sign for the Giants, whose rotation depth was thinned Friday when Anthony DeSclafani landed back on the 15-day IL with right ankle inflammation. DeSclafani missed two months with the issue before briefly rejoining the pitching staff last month, but he continued to feel discomfort in two subsequent starts, forcing the Giants to place him on the shelf for the second time this season.

It’s unclear how long DeSclafani will be sidelined, though Kapler said the 32-year-old right-hander felt he was “hitting a wall” in his attempts to rehab the nagging ankle injury. Asked if surgery is an option, Kapler said “everything is on the table.”

DeSclafani experienced some ankle trouble last year, as well, though he still emerged as a key member of the Giants’ rotation, going 13-7 with a 3.17 ERA over 31 starts. He re-signed on a three-year, $36 million deal over the offseason, but he’s been limited to only five starts so far this year, going 0-2 with a 9.95 ERA.

The Giants’ pitching depth will be tested in DeSclafani’s absence, as they’re currently entering a stretch in which they’ll play 17 games in the final 17 days leading up to the All-Star break. The staff should get a boost once Jakob Junis returns from a left hamstring strain, though they’ll likely have to lean on their bullpen to cover DeSclafani’s spot in the rotation in the interim.

“You’d like to have off-days spliced in there,” Kapler said. “It makes things easier, but we’re no different than any other team that doesn’t have a perfectly healthy rotation. Right now, we’ve got four healthy starters and that’s not the worst position to be in right now.”