The Giants’ young cornerbacks and safeties had each other’s backs when all hell broke loose. 

Now they have to come together to stop passes from flying over their heads, like happened in allowing three explosive plays. 

In a throwback practice against the Lions that was dripping with intensity, physicality and trash talk, the rebuilding Giants refused to be bullied Monday by the Super Bowl hopefuls during three sideline-emptying fights and a handful of other after-the-whistle skirmishes. 

“Seeing guys handling each other’s business, it goes back to adrenaline and knowing we are not backing down to anybody,” safety Dane Belton said. “No matter what happened last year, we’re coming to play.” 

Belton and the rest of the secondary of Jason Pinnock, Deonte Banks, Cor’Dale Flott and Dru Phillips — all 25-and-under starters in the NFL’s youngest secondary — as well as versatile supersubs Nick McCloud and Isaiah Simmons drew the difficult assignment of facing one of the league’s most explosive offenses, led by $212 million quarterback Jared Goff and First-Team All-Pro receiver Amon-Ra St. Brown. 

“You can’t run from it,” McCloud said. “If you don’t embrace it, it means you are not prepared.” 

Tensions boiled over quickly after St. Brown caught a pass against Phillips’ tight coverage.

Belton knocked the ball out of St. Brown’s hand just as the whistle blew.

St. Brown responded by shoving Belton in the facemask and Jameson Williams jumped in to shove Phillips in the back, which led to a full scrum and punches exchanged. 

“I was trying to finish a play and I feel like he wasn’t down, so I’m trying to get the ball out,” Belton said. “Everyone talks about [creating] turnovers, you’ve got to do things like that. People who know me, I’m not a big fighter after the play. I hate getting penalties because that leads to losing, and I love winning.” 

McCloud tussled with 6-foot-5, 335-pound All-Pro left tackle Peneii Sewell. 

“I wasn’t necessarily going after the biggest guy,” McCloud said. “They hit Dru and I feel like that was uncalled for. It doesn’t matter how big you are, I’m just trying to protect my guy. It’s nothing more than that.” 

The rookie third-round pick Phillips was warned by veterans to expect tempers to flare in joint practices on a hot day. The Lions jumped the Giants on the first day of practices last year. 

“It was a really good rep by me, so I kind of expected him to get mad,” Phillips said. “I’m a rookie, so I would think I just did my job well, maybe he just didn’t like it. At the end of the day, we’re just out there competing.” 

Phillips, who is in line to start in the slot, was at the center of a couple altercations. 

“[Tuesday] I just need to be more disciplined,” Phillips said. “I shouldn’t let myself get away from it like that. It’s kind of embarrassing, but be more disciplined, focus on play and just get back to doing what we do.” 

It was an early preview of how offenses might attack the defensive coordinator Shane Bowen’s scheme this season.

A menacing pass rush led by Dexter Lawrence, Brian Burns and Kayvon Thibodeaux could be neutralized if an opponent builds a big early lead through big plays downfield. 

Goff hit three long touchdowns when Daurice Fountain exploited a blown coverage in 7-on-7, speedster Jameson Williams left Flott in the dust as he crossed the field and then waved goodbye on his way into the end zone and Williams struck again from 20 yards out on a miscommunication between Banks and Belton. 

“It’s still early, but it’s not early. We’re right around the corner from the season,” Belton said. “There are some things we have to get in the film room and talk about. That goes to the difference in defenses from year-to-year. Before, we were in man [coverage] and there’s not much communication. Now it’s a lot of matches and when you do it right, it’s great.” 

The starting defense made its share of plays underneath, including an interception by linebacker Bobby Okereke, pass breakups by Pinnock and Simmons, a well-timed disruption by Belton and three straight forced incompletions in the red zone at the end of practice. 

“When you look back at practice today, it shows that we compete and can make plays against whoever,” Belton said. “We’re nasty, we’re dogs and we want to put it all on tape.” 

Burns left the field feeling confident that the “sticky” secondary is up for challenges like Tuesday’s rematch with the Lions. 

“That’s just growing pains. We can clean that up on the tape,” Burns said. “But it’s our job to make their life a little easier, put as much pressure on the quarterback as we can because we can. I think they’re going to bounce back. I like that group.”