Rondae Hollis-Jefferson has played all of 29 games in his NBA career; at 21 years old, he’s among the very youngest on a Nets team in the middle of a youth movement. And, beginning Wednesday, he’ll be tasked with helping take one of the worst defenses in the league and making it respectable.

All in a day’s work, huh? To his credit, Hollis-Jefferson hasn’t shrunk back. Not that it makes the task all that much easier.

“It’s tough, because it’s not only defense but energy, too,” acknowledged Hollis-Jefferson, who along with veteran forward Trevor Booker are the undeniable defensive leaders. “You’ve got to pick up full-court and hopefully your guys follow you as far as pressuring up, and stuff like that. Sometimes it’s tough, but I feel like it’s starting to rub off on the guys. Like when I pick up full-court, that means, hey, they’ve got to pick up and they’ve got to pressure up the guy with the ball, they’ve got to add in some denies. I feel like for the most part we’re going towards that.”

And while the stats don’t matter all that much in the preseason, there’s little denying that the defensive numbers were ugly. The Nets won only one game, their opener against the Detroit Pistons, and allowed an average of 111 points over six games. That wouldn’t be too much a cause for concern if they hadn’t had the third-worst point differential in the league last year (-7.4 per game).

The bright side is that the problems the Nets are facing this year are different from those they suffered through last season. And Kenny Atkinson seems to think these particular defensive issues can be solved with time. “I think we identified [the problem],” the Nets’ first-year coach said. “Rebounding has been an issue, transition defense, we need to improve there. So, we’re working on it . . . I would say defensively, we got 80 percent of our package of what we’re going to do. I think the challenge now is perfecting it.”

Hollis-Jefferson said it was a question of both familiarity and concentration.

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“It’s mental lapses,” he said, adding that there have been times early in games when the defense was where they needed it to be. “We’ve got to figure out how to keep it consistent, second quarter, third quarter, 48 minutes. Then, once we figure that out, we’ll be good . . . [When you’re tired] you might not think you have T-Book out there but you’ve got T-Book versus Justin Hamilton or vice versa. So it’s just understanding your personnel, who’s in the game, knowing how we’ve got to play.”

And if it’s any solace to the Nets, Hollis-Jefferson could easily be primed for a strong year. He was already making major contributions before fracturing his right ankle last season and should get plenty of playing time.

“He’s like a young leader,” Atkinson said. “We challenged him in summer league, even though you’re 21 years old, can you set an example for our young guys. Then we have that veteran group that he can look up to, but for him, there’s a group of players there that he can lead and I think he’s doing a pretty good job, a pretty good job setting an example.”