MINNEAPOLIS — Andrew Adams never had taken a regular-season defensive snap in the NFL. On Monday night, the undrafted rookie was the starting safety for the Giants against the Vikings.

It was the most glaring lineup change in a secondary that has been so battered by injuries that even the gallows humor of defensive coordinator Steve Spagnuolo wouldn’t hold up to scrutiny. Spagnuolo suggested this past week that cornerbacks coach Tim Walton, who played the position at Ohio State, might have to take a few snaps.

When it was pointed out that Walton is still recovering from offseason knee surgery, Spagnuolo could only shrug.

“That is a good point,” he said. “We can’t put him in there.”

The rest of the options weren’t much better. Adams, who was signed from the practice squad before last week’s game against Washington, played in place of the regular starter, Darian Thompson, out several weeks with a foot injury, and his backup, Nat Berhe, who suffered a concussion last week.

With Eli Apple inactive from a hamstring injury and Dominique Rodgers-Cromartie so limited by a groin injury that he could be used only as a reserve, Trevin Wade started at cornerback. Behind them was another undrafted rookie with no experience: Michael Hunter. Veteran Leon Hall was able to play a little bit of both positions.

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“This is what I have been preparing for my whole life,” Adams said. “Now the opportunity is presenting itself, so it is time to play football . . . It definitely happens fast. In this league, you have to stay ready. People go down and it is unfortunate, but it is the next-man-up mentality.”

Hunter nearly was that “next man” last week. He was promoted to the active roster for the practices leading up to the Washington game, then waived the day before the game (the Giants needed a safety more than a corner and they swapped Hunter for Adams).

“When you feel like you’re that close to actually playing in your first NFL game, it kind of hits you,” Hunter said. “It feels like it’s been taken away from you a little bit. You still have to realize that you’re blessed to be in this position. You have to stay ready at all times for every situation.”

For the first 2 1⁄2 games of the season, Spagnuolo was able to be creative with blitzes and pressures because he had such faith in his coverage. On Monday night, only Janoris Jenkins remained from that group he could count on.

“[They] have really allowed us to do some things that, quite honestly, you wouldn’t be able to do [without them],” Spagnuolo said. “When you can trust and rely on guys on the edge there, guys that can get things done that you need to do in this league, it gives you a lot of a lot of versatility inside and makes everyone else better. So we will miss them.”

The good news for the Giants, if there is any, is that they knew this was coming — unlike last week, when Apple and Rodgers-Cromartie were lost midgame.

“That was a challenge,” Spagnuolo said. “You look at the list [of plays] and half of it is gone because there were some things that we were going to do with a lot more defensive back bodies and we couldn’t do, so we had to get away from that.”

On Monday night, Spagnuolo was at least able to have an idea of his own limitations going into the game.

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“Does it make it any easier this week? I don’t know if it gets any easier,” Spagnuolo said. “[The Vikings] realize that we are down some guys. We will tweak some things a little bit and hopefully the guys that are going to go in there and play are going to be productive . . . We need to get somebody else to step up in there and hopefully they can get healthy quick.”

Notes & quotes: RB Rashad Jennings (thumb) missed a second straight game, leaving Orleans Darkwa as the starter for the first time in his career . . . Bobby Hart made his second straight start at RT with Marshall Newhouse inactive.