Awful defense already big issue for young Nets, Jordi Fernandez

The Nets are off to a historically bad start.

They’ve allowed 522 points over their first four games, the most in franchise history.

Bad defense isn’t terribly surprising for a Nets team that has the youngest roster in the NBA and is in a second straight season of tanking.

But that doesn’t make it any easier on head coach Jordi Fernández, who is trying to build a winning culture while — at the same time — the franchise looks to give itself the best chance of securing the top pick in next year’s draft.

So it’s left to Fernández — who called the defense “unacceptable” following Monday’s defeat — to sort out the details, like after the Nets gave up a season-high 137 points in Houston on Monday, with a home game on tap against the Hawks on Wednesday in Brooklyn.

“A lot of it is just lack of experience,’’ Fernández said after another lopsided defeat to the Rockets. “But we’re going to challenge them. The coaches are great and we’re going to find a way to challenge, to sustain the focus every possession. It doesn’t matter if you play 20 seconds, if you play three minutes, if you play 10 minutes, your attention to detail and your effort has to be there. And I know the guys will learn from it.”

Fernández had better hope so, otherwise he and his team will be in for an even longer season than anticipated.

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They’ve already allowed over 130 points in three of their first four games, something they “only” did seven times a year ago.

The 42 points scored by the Rockets in the first quarter was ugly enough, but then they saw Houston go on a 14-4 run to open the second half to put the game away, again thanks to shoddy defense.

“They [were] getting out in transition [and] no one was getting back,’’ Day’Ron Sharpe said of the porous defense. “We’ve got to talk better on defense … it’s just all the things on defense. We can’t have too many lapses of not talking or [being] in the wrong position.”

Fernández pointed to the early part of the third quarter as a consistent problem for his squad.

“The beginning of the third, it hasn’t been good,’’ Fernández said. “So that’s going to be addressed. Once again, it’s just a level of attention to detail and go there and put possessions together on both ends of the floor and just be better.”

And it’s not just that the Nets are being scored upon at an unprecedented rate.

No one else in the league is even close to being as inefficient on that side of the ball so far this season.

The 130.5 points per game they’ve allowed is the worst in the NBA, as is the 53.7 field goal shooting they’ve permitted to opponents.

And from 3-point range, it’s 46 percent.

“You give up 140 points, 50 percent [shooting] from the field, it’s not going to be good,’’ the coach said. “And right now, it’s the result that we deserve as a group. But I know we can do better. So … I keep working, [we’re] going to have positive energy and hold everybody accountable.”

Ziaire Williams, who missed Monday’s loss with a lower back/glute contusion, was listed as questionable for Wednesday.

And Egor Dëmin, rested as injury management for his left plantar fascia tear on Monday, was not on Tuesday’s injury report.