The San Francisco Giants entered Sunday tied with the Mets for the worst record in the National League and following another low point, a 13-3 home loss to the Pirates at Oracle Park, the fans in attendance let the team have it.

And the upset crowd had at least one backer: manager Tony Vitello, who is in his first season after taking the job following a successful tenure at the University of Tennessee.

“What would you do?” Vitello said when asked about the fans’ reaction. “They paid for their ticket. At the very least, even if it was free, they chose this over everything. There’s 85 million shows you can watch on Netflix, or in this city, I haven’t gone out much, but anytime I have, there’s a lot going on.’’

So he understood why the Giants’ faithful were not pleased in what’s quickly becoming a lost season by the bay.

At 15-24 heading into Sunday’s game against Pittsburgh, the Giants have lost nine of 11 games and scored the fewest runs in the majors.

And even though he’s in his first year in San Francisco, Vitello said he understood what’s at stake.

“Whether you paid for your ticket or you just chose to do this over other options — or maybe your walls are painted orange and black and this is the team your whole family for generations has supported — you’ve got a lot invested,” Vitello said. “So you want something in return. At the very least, a good effort, maybe execution here and there. … It got to the point where it wasn’t an acceptable effort, so they probably did what you or I would maybe do.”

They recently came off a seven-game road trip in which they didn’t win a game and things haven’t improved much at him.

And after finishing their homestand on Sunday, the Giants head to Los Angeles to face the Dodgers for four games.

It’s hard to see how the season gets better. The Giants recently traded Gold Glove catcher Patrick Bailey to Cleveland in exchange for a draft pick and a prospect and seem to be heading in the wrong direction. They also called up a pair of prospects, Bryce Eldridge and Jesus Rodríguez as president of baseball operations Buster Posey tries to salvage the season.