The starting center for the Giants was veteran Ben Bredeson — on Day 1 of training camp.

Significance?

Well, the starting center for the Giants on Thursday, Day 2 of camp, was rookie John Michael Schmitz.

Get used to this.

There will be flip-flopping of players with the first and second teams throughout the summer.

“I think we talked about this last year quite a bit, relative to the rotation for the offensive linemen,’’ coach Brian Daboll said. “You will see, I would say, a good amount of rotation on a day-to-day basis. Sometimes on a period-to-period basis.’’

So, a player working with the starters in the 7-on-7 drill might not be with the starters later in the day in the team period, and vice versa.

Schmitz, a second-round pick from Minnesota, is expected to make a strong push for the starting job.

“He’s a smart guy, he works hard,’’ Daboll said. “There’s a lot, as you know, on your plate, playing center. He’s very cerebral, he’s intelligent. He’s made progress since he’s been here.’’

The Giants went through the entire spring offseason workout program without Saquon Barkley, who did not participate in the voluntary work because he had not signed his franchise tag.

He was missed.

“A lot of respect for him,’’ DT Dexter Lawrence said. “I’m happy he is here. He challenges everybody on the team in a way that he doesn’t even know half of the time.

“He brings a good attitude. I’m just happy he’s here and he’s working hard. He’s pushing people to get better, and he’s continuing to grow.’’

Daniel Jones and the passing attack came out flying Wednesday, but the coverage was tighter and more footballs hit the ground Thursday.

“We had a really good Day 1,’’ WR Darius Slayton said. “[Thursday] we had a good day. I feel like we picked it up towards the back end half of practice. We didn’t start quite as fast as we wanted to, just from an execution standpoint. But all in all, I think we had a good first few days.’’

DT Rakeem Nunez-Roches sat out again after he was involved in a car accident near the team facility after leaving the building Tuesday. Nunez-Roches came away from the scene with a concussion.

“He’s sore,’’ Daboll said. “It could have been worse, so I’m glad he’s where he is right now. I think he’s making progress.’’

Daboll said he does not believe Nunez-Roches will be out for an extended period of time.

The Giants signed DT Kevin Atkins, who went undrafted out of Fresno State and spent last offseason with the 49ers. He most recently played for the XFL’s St. Louis Battlehawks.