SANTA CLARA, Calif. — They all proceeded, grim-faced, to the team bus after the latest in a season saturated with embarrassing moments — 49ers 31, Giants 21 on Sunday at Levi’s Stadium.

When Giants coach Ben McAdoo got to the bus, he was admitted on board without incident. Same for general manager Jerry Reese, who declined to speak to reporters when asked on his way out of the locker room.

Why is this relevant?

Because, based on the quality of the product McAdoo and Reese oversaw on the field Sunday, you couldn’t have blamed Giants ownership if they’d barred their head coach and GM from entering the bus, instead leaving them to cab it to the airport and fly middle-seat coach cabin back to Jersey.

But you can bet the thought ran through the disillusioned minds of John Mara and Steve Tisch.

The Giants owners are not going to do this, because it’s never been how they operate, but this thing has gotten so bad with this Dead Team Walking that it feels like they need to make a coaching change.

Not after this season.

Now.

If you wondered if this lost season could possibly sink to a lower point than it did last week when the Giants lost 51-17 to the Rams at home, wonder no more. Enter Sunday’s unthinkable embarrassment against the previously winless 49ers as Exhibit A.

It simply cannot get worse than this. Can it?

The 49ers entered the game with the NFL’s worst record at 0-9, with a league-high 23 players on injured reserve and so concerned about how bad their team is they’re afraid to play Jimmy Garoppolo, their prized franchise quarterback acquired last month in a trade with the Patriots, for fear of getting him hurt.

“It’s definitely shocking to lose to that team that we just lost to,” Giants offensive lineman Justin Pugh said. “I thought we were going to win today for sure. Losing to an 0-9 team … it can’t get much worse than that.”

The 49ers entered the game having scored 10 points in each of their previous three games, getting outscored 93-30 in that span. They topped their three-game total Sunday against a Giants defense that simply looks like it doesn’t care anymore.

“It’s embarrassing,” defensive end Olivier Vernon said.

“To be honest, I didn’t see enough want-to,” cornerback Dominique Rodgers-Cromartie said. “I didn’t see enough relentless play, attitude, you name it, I didn’t see it. One team came out swinging harder than the other. We come out flying around and somewhere it dies.

“What can you say? We know what kind of performance we went out there and put. I’m embarrassed for us. We cannot continue, week in and week out, to go out there and put a performance like that.”

Rodgers-Cromartie wasn’t intending to indict his head coach with what he was saying, but his words were damning. They described a team that has stopped playing. It’s a reflection of the head coach and his inability to turn the bad football around.

McAdoo looks and sounds like a coach who has no answers, and that’s not a good reflection on him. The optics are terrible, and they’re only going to get worse from here, with NFC East home games against Washington, Philadelphia and Dallas still to come.

McAdoo responded to nine different questions in his postgame press conference by referring to his need to watch “the tape.’’

“We need to go take a long, hard look at the tape,’’ he said, “and be honest with each other.’’

To be as honest as we can here, that was a cop-out by a coach who knows exactly what he saw on the field Sunday and doesn’t need to look at the tape to decipher and diagnose the damage.

The wisdom in firing a head coach in midseason usually is driven by one of two things: Lighting a fire under a dead team with hopes of turning the season around or having an assistant on the staff ownership might want to take a look at before the end of the season.

The complication for the Giants is twofold: At 1-8, their season is done with little left to accomplish in the final seven games, and there isn’t an assistant on the Giants staff who’s even a remotely legitimate candidate to replace McAdoo.

If you want to make the argument McAdoo oversaw an 11-5 team that went to the playoffs only a year ago, consider how far this thing has fallen since then and ask yourself if he looks like a guy who’s going to turn it around?

“I never saw a coach get fired after an 11-6 season,’’ safety Landon Collins, a staunch McAdoo supporter, said. “I’ve never seen that before and it shouldn’t happen this year.’’

Except that it should. End it now. Get it over with. Reboot. And move on.