This summer, Nets general manager Sean Marks gave coach Kenny Atkinson some great pieces to work with. Now Atkinson must figure out how to fit them together.

The Nets opened training camp a week ago, but the process doesn’t really start until Friday’s preseason opener at Barclays Center against Sesi/Franca.

“We’ll see how everybody plays Friday,” Joe Harris said. “That’s why you have these preseason games. That’s why you have training camp.”

Practice can’t replace live action, even if it is against an outmatched Brazilian club.

“No, we’ve got to see them … more, and then we’ll make adjustments off that,” Atkinson said.

“Just get a feel for the team, the guys and the rotations and guys playing together. Where guys are. Where are we with our system? We want feedback now. … We’ve battled each other and had an intrasquad scrimmage [Wednesday] and got feedback there, but the best feedback is a real throw-it-up-and-play game.”

When the Nets finally throw it up and tip off against Franca, they won’t have free-agent signees Kevin Durant and Kyrie Irving.

Durant is out with a ruptured Achilles, while Irving has had just two full practices since returning Tuesday from facial injuries suffered in a pickup game. It’s unclear how the Nets will use Irving in the preseason. What is clear is they’re focusing on defensive principles first. After their infusion of talent, the Nets are confident the offense will come.

“It’s your defensive system. … That’s No. 1,” Atkinson said. “No. 2 is our offensive principles. Knowing that the defense is going to be ahead of the offense a little bit … maybe you’re accepting a little more lack of execution for lack of a better phrase.

“But definitely the defense is No. 1, see where we are there. … And then it’s getting to know the personnel better, especially the new guys, where they fit best with what we’re doing.”

Frankly, there are a lot more new guys than returning players. Thirteen of the 20 players in camp weren’t with Brooklyn last season. That kind of turnover — and next week’s trip to China cutting into practice time — is why the Irving-led workouts in Los Angeles this summer were so vital.

“What we did a little bit earlier on that I’ve done in the past few years, which has been to get together all of August and heading into September,” Irving said. “We’ve been together having open gym for a while now. Obviously it’s still game-like that we have to get used to.But it’s really fun just to be out here with the guys officially starting this.”

The Nets will depart Sunday for China, where they’ll play the Lakers in Shanghai on Oct. 10 and in Shenzen on Oct. 12. That pushed up the schedule and cut into camp.

“Because we have so many new faces, we have to come back and build our foundation and our core principles,” Atkinson said. “We’re really building our foundation. That’s where we are, build our system. So really it’s back to square one and building out from there.”

Those principles are going to start with defense. It’s where last season’s turnaround began, and it’s what any future rise and hopeful contention are going to have to be based on.

The Nets’ offensive rating last season dipped slightly from 16th in the NBA through Dec. 7 to 20th over the rest of the season. But their defensive rating shot all the way up from 22nd to eighth. That’s what let them turn a sorry 8-18 start into a red-hot 34-22 finish and a playoff berth.

“My concern is on the defensive end,” Atkinson said. “We were better defensively last year than offensively. That’s a concern: Where are we going to be defensively? Are we going to be able to improve on last year’s defense? It’s going to take some time, but I think we’ll improve offensively.”