Ben McAdoo won’t be remembered for much as an NFL head coach. His calamitous second season with the New York Giants is winding down, and he is giving the franchise’s patient owners little choice but to oust him at season’s end. But he will be remembered for one thing: He is the coach who sat Eli Manning.

McAdoo’s stunning announcement Tuesday that Geno Smith, not Manning, will start at quarterback Sunday at Oakland brought a prosperous Giants era to an unofficial close. The Giants won two Super Bowls with Tom Coughlin as their coach and Manning as their quarterback, twice upsetting the New England Patriots in memorable fashion, to close the 2007 and 2011 seasons.

But McAdoo replaced Coughlin as the team’s coach before last season, and now he has ended Manning’s streak at 210 consecutive regular season starts.

“I have a lot of confidence in Eli as a player, as a quarterback,” McAdoo said at a news conference Tuesday. “But at this point, it’s my responsibility for the organization to make sure we take a look at Geno and at some point take a look at Davis [Webb, a rookie third-string quarterback] and give them the opportunity to show what they can do heading into next year.”

McAdoo said he pondered the move after the Giants’ feeble 20-10 defeat Thanksgiving night to the Washington Redskins at FedEx Field. The defense scored the Giants’ only touchdown in that loss, which dropped their record to 2-9. McAdoo spoke to Manning on Monday and again early Tuesday, and Manning declined McAdoo’s offer to keep the starting streak going by having Manning play the first half and having Smith take over for the second half.

“Our number one job is to still win football games,” McAdoo said. “But it’s my responsibility to make sure we have a complete evaluation of the roster top to bottom, especially at the quarterback position, moving on to next season.”

In truth, this isn’t about evaluation. Smith almost certainly is not the Giants’ successor to Manning. It’s unlikely that Webb, a third-round draft choice this year, is either. Manning’s successor probably will come via next year’s NFL draft, in which the Giants should have a lofty first-round pick, based on this season’s ugly results.

This was about, in effect, cutting the franchise’s emotional ties to Manning sooner rather than later, and about beginning what now appears almost certain to be an offseason housecleaning. It is difficult to envision McAdoo or the coach who follows him turning back to Manning.

Manning, as he spoke to reporters Tuesday, was asked whether he believes he has played his final game for the Giants.

“I don’t know,” he said. “I don’t know. I’ll take it one week at a time.”

He was obviously emotional as he said, “It’s hard. It’s been a hard day to handle this. But I’ll hang in there and figure it out.”

Manning was asked if this was his toughest day with the franchise that obtained him in a draft-day trade with the Chargers in 2004 orchestrated by Manning, his family and agent Tom Condon to keep him from playing in San Diego.

“It’s up there,” Manning said.

Those from in and around the league jumped to Manning’s defense.

“Eli Manning has been totally disrespected by the Giants,” former Redskins linebacker London Fletcher, another NFL iron man, wrote on Twitter.

Former Giants offensive tackle David Diehl wrote on Twitter that he was “absolutely speechless” and questioned whether “this [is] what you do to a man who has [led] this team for 210 straight games[.]”

But some saw it coming. Former Redskins quarterback Joe Theismann said earlier this month that the end for Manning with the Giants was in sight.

“The Giants under Eli won two Super Bowls because of the way Eli played during the playoffs,” Theismann said then. “Those were teams that were not dominant teams, by any stretch. He deserves all the credit in the world for those two Super Bowls. But this has been going on for a while. It doesn’t just start in one year. I do think we’re seeing the end for him in New York with the Giants. I really do.”

McAdoo said he spoke to Giants General Manager Jerry Reese and the team’s ownership and that everyone was “on the same page” with the move. McAdoo said the benching of Manning “has nothing to do with my future.”

For McAdoo, that coaching future with the Giants could be short-lived. McAdoo guided the Giants to the playoffs last season as a rookie head coach. But the team has fallen apart this season. The effort level of McAdoo’s players during games has been questioned. He has suspended two players for violating team rules. The team appears in disarray on McAdoo’s watch. Now things have deteriorated to the point that Manning has been benched.

Giants co-owners John Mara and Steve Tisch are known for their patience. But would anyone be patient enough to bring back McAdoo for another season?

“Listen, I haven’t coached well enough,” McAdoo said Tuesday. “Our offense hasn’t played well enough. Our defense hasn’t played well enough, and our special teams haven’t played well enough. All those reasons are why I’m standing here right now. They’re all part of it.”

When McAdoo took over for Coughlin, he spoke of it being an evolution, not a revolution. Instead, it has been a ruination.

This day was coming . . . eventually. It came for Manning’s brother Peyton in Indianapolis. It even will come for Tom Brady in New England. It comes for all NFL players, even the greatest quarterbacks. But the deterioration of the Giants under McAdoo hastened it and made it far less dignified than it could have been.

The overhaul of the Giants has begun. They could have a new GM, new coach and new quarterback in place by Opening Day next season. More major changes probably are in store. But nothing that is yet to come will be more significant than what happened Tuesday.

“I think a lot of Hall of Fame quarterbacks who have done a lot for a lot of teams haven’t been able to choose the way that they get to move on,” McAdoo said. “And I’m not saying that we’re moving on. But at some point in time, you have to make hard, tough decisions for the best for the franchise. That’s what I have to do here.”