Duke’s Zion Williamson, expected to be one of the top freshmen in the NCAA next season, is listed at 6-foot-7 and 285 pounds.

Williamson ranked No. 5 overall in our first aggregate mock draft for next season. As noted by Bleacher Report’s Jonathan Wasserman, his weight is more than any player in the league besides Boban Marjonovic. However, his size has remained relatively similar to what he weighed (272 pounds) back in October 2017.

The 18-year-old forward can use his massive frame to dunk over any player he has faced thus far. While we know he has an incredible leaping ability, we’ve not yet seen him play against top collegiate talent. He got hurt during the All-American game and did not participate in the Jordan Brand Classic or the Nike Hoop Summit, where we could have seen how his size matches up against similar prospects.

David Nurse, an NBA trainer who works with players on all aspects of their life including nutrition, believes Williamson must create good habits early for this size to work for him during his career.

“He’s sort of built like a LeBron James-type. But whether he can be highly effective in the NBA with that body type will come down to his commitment to himself,” Nurse said. “He needs to understand nutrition and every little aspect of taking care of himself. He has a body type that could very easily balloon up.”

James, for comparison, was believed to weigh as much as 280 pounds during his heavier days in Miami. But he was listed at 250 pounds when he returned to Cleveland in 2014. Others have compared him to Basketball Hall of Fame big man Charles Barkley.

According to one NBA trainer who spoke off the record because they were not authorized to speak publicly on the subject, Williamson should probably have a personal chef and must be “obsessive” about his own self-regulation.

“Heavy daily cardio or bouts of strict dieting will break his body down over time and make him more injury prone,” the trainer said. “The last thing he wants to do is play all year at a heavier weight and then crash downwards toward the NBA Combine and Summer League. This will set back his first two years, mentally and physically. This is always bad long-term, even though the pictures are pretty at the Combine.”

A second NBA trainer also spoke off the record because he cannot talk to the media. He said Williamson must learn everything there is to know about nutrition in order to become the explosive player many hope he’ll be at some point. Otherwise, there could be severe consequences.

“If he plays heavy and his weight and habits fluctuate, he will be dancing with the devil,” he said. “Any poor performances or injuries will be blamed on his weight, and he’ll also have to reinvent his game after each injury. Those are some of the psychological factors he’ll have to deal with too.”

A third trainer, who also spoke off the record, believes that as long as the Duke prospect can run and jump on that weight he will be fine if there are no issues with his knee.

Jumping certainly won’t be a problem for the South-Carolina-born phenom. Duke’s Twitter account reported that Williamson set a Blue Devil record for the best vertical leap in school history. According to USA TODAY’s Jason Jordan, he maxed out at 46 inches. That would be on par with dunkers like Zach LaVine and Jason Richardson for best in NBA history, too.

Finally, we touched base with an NBA assistant coach, who spoke off the record because he is not authorized to speak publicly on the matter.

“If you’re playing 82 games at that weight, running up and down the floor, that’s bad for his joints and it’ll take a toll on him. I think he’s going to struggle with a lot of things. If it were me, I wouldn’t play over 260-to-265 pounds if I was 6-foot-7. In today’s game, with every team getting out in transition, with more possessions than ever before, it’s concerning if a guy is carrying that much weight.”

It’s unclear what his body fat percentage looks like but recent photos also do suggest he has a ridiculously muscular frame, built almost like a linebacker.

Nurse, meanwhile, provided more details on how Williamson can stay in shape as he continues his basketball career.

“It’s important that his team stresses a healthy diet and creates good habits because NBA rookies don’t always make the right decisions when it comes to the food they’re eating. Many players don’t realize how important that is until they get a little bit older.

“He needs to understand these things now because that will be the difference between him staying 285 pounds and being lean and mobile with that big body or weighing too much and pulling a Vin Baker. He’ll have a lot of choices that he’ll have to make in order to take care of himself. Zion is very talented and athletic, but he has a big frame that he has to deal with.”

The assistant coach, however, compared him more to Boston’s Guerschon Yabusele, who is a heavier player. The coach noted that speed, quickness and agility are what teams prefer to see. It will be fascinating to see how college and NBA coaches develop the prospect as he transitions to the next level.

Even though Williamson can overpower people, this coach would much rather see him trim his weight so he can be quicker on his feet and switch onto smaller defenders. The coach is worried about his first step and how he would match up guarding someone on the perimeter.

“The big thing for Zion is going to be slimming down during his season at Duke,” said the coach. “Every team in the league is going to be looking at his body fat percentage and weight during the pre-draft process. If he’s able to slim down a lot, that could help him. It’ll show teams how committed he is and how much he loves the game.

“But if he doesn’t slim down, I’d be worried about how effective he can be in the NBA. Dunking over high school kids who are way smaller than you doesn’t mean you’ll be able to make it in the NBA, where everyone is bigger and more athletic.”

HoopsHype’s Alex Kennedy helped contribute to this report