Pete Alonso broke his bat over his knee in disgust after striking out in the third inning against Conner Menez, but said his frustration was over that particular at-bat, not anything bigger.

“I was just upset because I shouldn’t have swung at that pitch — it was a ball,” Alonso said after the Mets lost 3-2 to the Giants in 12 innings in San Francisco on Sunday. “I know I am better than that. I hold myself to a high standard and I was just frustrated.”

Michael Conforto’s “splash hit” that landed in McCovey Cove was the 47th such home run by an opponent in the history of Oracle Park. Curtis Granderson had been the last Mets player to homer into McCovey Cove, on Aug. 19, 2016 against Johnny Cueto.

The Mets’ 44 home runs on the road since June 1 lead the major leagues.

Adeiny Hechavarria started at second base to give Robinson Cano a day off. Hechavarria went 0-for-4 with a walk and a strikeout.

The Mets, in conjunction with the New York Blood Center, will sponsor their semi-annual Blood Drive on Monday from 11 a.m. to 6 p.m. at Citi Field. All donors will receive a voucher redeemable for two tickets to a select Mets home game.