Eli Manning showed up for an official day of work Monday and, for the first time in his NFL career, Tom Coughlin was not there as his coach.

Shocking?

Not really, the quarterback said after the opening day of the Giants’ voluntary offseason program and, in many ways, the opening day of the Ben McAdoo regime.

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“I guess it sunk in a little bit just because the last few months, I’ve been doing a good bit of training at the Giants’ facility,” Manning said at the dawn of his 13th season. “So I’ve gotten to know Aaron [Wellman, the new strength and conditioning coach] a little bit, gotten to see Coach McAdoo walking down the halls. Just understand that he’s the head coach now and not the offensive coordinator. I think it probably wasn’t as big of a shock, the total difference, to the start of the offseason today as what it could have been.”

For others, though, this was their first taste of the new normal. The Giants have made a number of changes since the players were last together in a formal setting in early January, including a revamped weight room and some different inspirational slogans hung on the walls.

“It’s definitely new,” guard Justin Pugh said.

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So, too, are the faces. The Giants invested millions in free agency, and this was the first time those purchases were able to mingle with the players who are returning.

“I’m just trying to remember names and everything right now, that’s the whole process,” new defensive end Olivier Vernon said. “This is kind of like rookie year in the NFL. You have to learn the whole playbook all over again. New coaches, new players, but you kind of have a little step ahead of the game from your rookie year, because of how many years you put in. You have some knowledge of the game.”

As for the most glaring change — the head coach — it was the first opportunity for the players to see McAdoo in that role. “I was curious as to how it would be, but he’s Coach McAdoo,” center Weston Richburg said. “He does a great job of staying who he is, staying true to what he believes. As a player, that’s really exciting.”

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“The offense, I think we’re kind of used to the way McAdoo approaches things, how he communicates with us,” Pugh said. “I think it was more for the defense really meeting him and getting to know a lot more about him, because a lot of the things the offensive guys have seen throughout the course of the [two] years we’ve had with Mac already.”

Manning said McAdoo addressed those who attended the voluntary workout — nearly the entire team — and spoke about the goals of the season and the style of play he wants to see.

“I think any time you change things up, you have new things going on, it can give you that fresh start,” Manning said. “There’s an urgency to kind of get things corrected, get things going the right way, make sure you’re on the same page with everybody.”

After one day, at least, the word on that page seems to be optimism. Monday showed that things are different; it won’t be until September that we’ll find out if they are better.

“I am excited,” Manning said. “I think guys sense that we have a good squad, that we have the capability to win a lot of football games, that we did some really good things last year.”

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Notes & quotes: Defensive tackle Johnathan Hankins, who missed the last seven games last season with a torn pectoral muscle, said he is “pretty much fully healthy and full go” for the offseason program . . . Newly signed linebacker Kelvin Sheppard is a first cousin of Giants wide receiver Dwayne Harris. Besides Sheppard, the Giants signed running back/kick returner Bobby Rainey and tackle Byron Stingily on Monday.