Tony Vitello was handed a gift on a silver platter, and he somehow mistook it for a live grenade.

The Giants’ rookie manager, straight out of the college ranks, had a perfect, frictionless opportunity to establish his authority in a big-league clubhouse. All he had to do was staple Willy Adames to the bench for one night.

On Wednesday in L.A., with runners on first and second with one out in the seventh against a to-that-point dominant Shohei Ohtani, Adames forgot the number of outs after being caught chatting up Mookie Betts before Drew Gilbert’s deep fly out to left-center field. He was chugging around third base and heading home by the time the ball was relayed to second for an easy danger-ending, Ohtani-saving double-play.

It was the Giants’ best chance to score in a game they ultimately lost 4-0.

It was downright unacceptable, unquestionably inexcusable carelessness; the kind of play that wouldn’t fly in even a high school game.

You couldn’t have written a better script for the new manager. Adames wore the mistake like the pro he is, admitted he screwed up, and practically conceded he should be benched for it. There was no explaining away a mistake like that. He apologized and said he’d respect any decision the manager made regarding his playing time on Thursday.

The college coach had an easy pro win.

But Vitello blinked. He, like so many other Giants this season, whiffed.

Adames started Thursday’s game.

It was the simplest test of Vitello’s young major league career, an open-book quiz on Clubhouse Management 101.

When your highly-paid veteran shortstop turns a crucial, rare offensive spark into a punchline because he’s distracted by idle gossip with the opposition, you sit him down for a day. You make an example out of him, just as you would the last guy on the roster. You take a stand for playing the game the right way and keeping your head in the proceedings.

It isn’t about malice; it’s about the standard.

Benching him on Thursday wouldn’t have been an act of vindictiveness, just as playing him wasn’t an act of mercy.

Vitello’s justification for playing Adames?

“I want to win the game today is why he’s in the lineup,” Vitello said.

How’d that work out?

The Giants lost 5-2.

And Adames? He went a robust 0-for-3 with two strikeouts. The baseball gods have a wicked sense of humor, but they rarely miss the mark.

Vitello is the fiery college coach trying to find his footing — and his fire — in the big leagues.

It’s an unprecedented transition that’s proving to be as tricky as expected — perhaps even trickier.

In the SEC, Vitello was a dictator, a fiery lord of the dugout who could bench a kid for a bad haircut. His Tennessee teams might have boasted big personalities, but they weren’t joking around on the diamond.

In the big leagues, managers are diplomats, navigating egos worth more than the GDP of a small island nation.

But diplomacy doesn’t mean total abdication of duty.

Right now, Vitello looks less like a manager and more like a substitute teacher.

Adames wouldn’t have fought a benching. Even if he had a big ego (he doesn’t), what footing did he have here?

His heart might be in the right place, but his head was floating somewhere in the stratosphere, presumably discussing “the pod” with Mookie.

A day on the pine wouldn’t have caused a mutiny. It would have been met with a collective, silent nod from the rest of the roster.

Adames would have paid his playing-time penance (as well as a fine to the team’s kangaroo court — perhaps funding a postgame pizza party), and everyone would have moved on from the mistake.

Instead, Vitello’s inaction speaks volumes. And it has a real chance to linger.

Because it tells the roster that careless play carries no consequences.

It tells the veterans that the new guy doesn’t have the stomach for big-league discipline.

And it tells fans there is no baseline standard of play the Giants are trying to uphold.

You can cross the line, but if it’s an honest mistake and you’re a good player (though Adames’ numbers stand in stark contrast to that concept), they’ll just move the line for you.

Vitello had a layup. He had a chance to assert himself in the pros; to show he isn’t just happy to be here. (If he is.)

He didn’t have to scream. He didn’t have to throw a chair. He merely had to tap the brakes on Adames’ playing time for a day, embrace the awkwardness for a few innings (he could have put him in as a defensive replacement — this is slap-on-the-wrist stuff), and let the silence do the talking.

Instead, he opted for the path of least resistance.

It was a weak move from a manager who was sold as anything but passive. A manager who, a quarter of the way through the season, has yet to put his stamp on the team in a positive way.

But in a negative way? After Thursday, that’s a conversation.

Because if Vitello can’t handle a simple case of a star player forgetting the outs at a critical juncture of the game against an archrival, who is to say what will be accepted next for a team that’s already flirting with effective playoff elimination?