The spiraling Giants, fresh off a blowout loss, turned to their rookie starting pitcher to help them secure a much-needed series win. On the road. Against one of the best teams in baseball.

With a loss, the team would reach a new low.

Hey, no pressure.

Carson Whisenhunt (W, 5 1/3 IP, 3 H, 2 R, 1 ER, 2 BB, 4 K) toed the rubber for San Francisco (56-56) against the mighty New York Mets (63-49) on Sunday at Citi Field, and gave the Giants, with the help of an offensive outburst, exactly what they needed on the mound in a 12-4 win.

“I thought it was good,” Giants manager Bob Melvin said of Whisenhunt’s outing postgame. “To be able to go out in the sixth, [against] a lineup like that? I had to go get him, but he only gave up three hits. His fastball he spotted a lot better, which is going to be really important for him. You can feel, sometimes, teams sitting on his changeup just because it’s kind of well-advertised before he goes out there. Same thing as last outing.

“… In a game like this, it’s a big game for us to try and win a series and he was right at the forefront of it.”

Whisenhunt, the Giants’ top pitching prospect, made his MLB debut in San Francisco’s 6-5 loss to the Pittsburgh Pirates on Monday, and while his overall line (5 IP, 5 H, 4 ER, 2 BB, 3 K) was nothing that impressive, fans got their first glimpse at the 24-year-old’s elite 65-grade changeup, which fooled both Mets hitters and Whisenhunt’s teammates behind him on Sunday.

“That changeup is … that thing goes backwards,” second baseman Casey Schmitt told NBC Sports Bay Area’s Laura Britt and Shawn Estes on “Giants Postgame Live.” “That thing is unbelievable. But I’ve seen him throw a lot, played with him in Sacramento. He’s got great stuff and you all saw it today. For him to go out there and do his thing like that out here in New York, it was a special game.”

Whisenhunt surrendered a solo home run to Mets slugger Francisco Lindor in the bottom of the first, and an RBI double — an unearned run due to a Giants error — to Francisco Alvarez in the bottom of the sixth before his departure with one out.

“It was a great atmosphere,” Whisenhunt told reporters postgame. “That’s probably the biggest thing, everybody was screaming, which I enjoy that. Obviously they’ve got a good lineup, but not overthinking or trying to do too much. Just enjoying the moment and trying to help the team win.”

Other than a couple of mistakes, it was a pretty clean day for the rookie, who was greeted with a postgame beer shower in the team’s clubhouse.

“Everybody was screaming, congratulating me and everything, and then the beer shower. So that was fun,” Whisenhunt said when asked about the postgame celebration. “Not too bad, so I’ll take it.

“There was some applesauce and some milk thrown in there, but no mustard or ketchup or anything. Thank the lord.”

Still gross. But earned.

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