Jacob deGrom is accustomed to getting shafted by his own team, but now the umpires are potentially damaging his National League Cy Young award candidacy, too.

With each pitch thrown by the Mets’ ace under scrutiny as he battles Max Scherzer and Aaron Nola for the coveted prize, deGrom received a raw deal from home plate umpire Tony Randazzo on Thursday before the Mets’ lineup piled on in a 3-1 loss to the Giants and their stud lefty, Madison Bumgarner, at Citi Field.

DeGrom (8-8) lasted six innings and allowed two runs — one of which was unearned — on four hits and four walks with 10 strikeouts. He departed after 108 pitches with his ERA exactly where it was to begin the day, at 1.71.

But deGrom was rightfully steamed in the fourth inning and began screaming at Randazzo after Bumgarner stroked an RBI double that gave the Giants a 2-0 lead. The previous batter, Nick Hundley, had walked after Randazzo missed the call on an 0-2 pitch that should have been Strike 3 to end the inning.

“I was frustrated, but I still have got to make a pitch there,” deGrom said. “That made it 1-2, so I had three more pitches to make a pitch, but I wasn’t able to do it.”

DeGrom was asked what he screamed at Randazzo.

“I told him, ‘You can’t miss it,’ ” deGrom said. “I thought it was a strike and you can’t miss that. Nobody is perfect out there and just like we make mistakes, leave balls over the middle and they get hit, you can’t expect them to be perfect.”

Randazzo, a 19-year veteran, declined a request from reporters for comment.

DeGrom’s chief competition in the Cy Young race, Scherzer and Nola, faced each other in Washington. Nola pitched eight scoreless innings and lowered his ERA to 2.13. Scherzer carried a shutout into the seventh before allowing a two-run homer to Odubel Herrera and saw his ERA inch from 2.11 to 2.13.

Bumgarner was brilliant for the Giants, allowing one run on five hits over eight innings. The ace lefty improved to 6-0 lifetime with a 0.59 ERA in six career starts in the Citi, including postseason. Bumgarner had a 33-inning scoreless streak at Citi Field conclude on Todd Frazier’s homer in the seventh.

Randazzo’s first questioned call came in the third, when Evan Longoria’s swing and miss wasn’t ruled a foul tip and the ball eluded Devin Mesoraco for a passed ball that allowed a run to score. Mesoraco argued Longoria made contact, and manager Mickey Callaway also contested the call. DeGrom’s sin in the inning was walking the first batter, Steven Duggar.

Overall, deGrom has allowed three runs or fewer in each of his past 23 starts — one shy of the franchise record set by Dwight Gooden in 1985.

“To get through six innings, 10 strikeouts, to keep us in the game, he did an unbelievable job,” Callaway said. “He probably didn’t have his best fastball command, but he’s such a good pitcher that he has other ways to get you out so it’s not success that hinges on whether he has got just fastball going.”

Frazier homered leading off the seventh to pull the Mets within 2-1, but Bumgarner escaped further trouble as Kevin Plawecki hit into a double play to help crush a rally before Michael Conforto struck out for the third time, leaving the tying run at third base.

Longoria homered against Tyler Bashlor leading off the eighth to put the Mets in a 3-1 hole.

DeGrom was asked if his frustration with Randazzo’s missed strike call pertained to a Cy Young race that likely won’t be decided until the final month.

“It had nothing to do with the Cy Young,” deGrom said. “It has to do with being out there competing. You make a pitch and you think it’s a strike and you want it to be a strike and it wasn’t.”