When you see your little brother — who’s in sixth grade — dunk a basketball, you have an epiphany.

“I was like, all right, he has the workings to be a good player, for sure,” said Hunter Flagg, older brother to Cooper Flagg, who on Wednesday night will join an exclusive club that includes Kareem Abdul-Jabbar, Bill Walton, Magic Johnson, Patrick Ewing, Tim Duncan and LeBron James. “When you’re growing up, seeing him being successful at every level of play, it’s pretty surreal.”

Unless the Dallas Mavericks screw things up in historic fashion, Cooper Flagg will be the first player selected in the NBA Draft at the Barclays Center in Brooklyn.

ESPN draft analyst Jay Bilas, who knows college basketball and the draft as well as anyone, said Dallas will not screw this up.

“There are 30 teams in the NBA, and all 30 would take Cooper Flagg,” Bilas said last Friday morning before he took part in the Drive Fore Kids golf tournament at Falmouth Country Club. “I get it, this is the speculating season on trades, but I can’t imagine that Dallas would even trade that pick. Flagg is the future of that franchise. They’ve got a good present as long as Kyrie Irving gets healthy at some point in the season. (Flagg is) the future; they’re not going to trade that.”

This is what excitement in Maine has been building up to for a few years. From Flagg’s one year at Nokomis High, when he and his twin brother, Ace, led the Warriors to a Class A championship, to Montverde Academy, to one season at Duke. It’s all been prelude to hearing NBA commissioner Adam Silver announce Flagg’s name in the NBA Draft.

Vince Carter also took part in the Drive Fore Kids golf tournament. He was selected with the fifth overall pick in 1998 out of the University of North Carolina, and went on to a 22-season NBA career. Asked what advice he wished he had been given when he was entering the league as a rookie 27 years ago, Carter had to think.

“I got all kinds of good advice because when I came in (the NBA), that’s when guys were helpful,” said Carter, who will work as a studio analyst for NBC next season. “Just be himself. Being the No. 1 pick, he’ll have all kinds of pressure just from that. He needs to be himself, and have fun.”

What sets Flagg apart from the rest of this draft class is his basketball IQ and mental approach to the game, Bilas said. Flagg led Duke in scoring (19.2 ppg), rebounds (7.5 rpg), assists (4.2 apg), steals (1.4 spg) and blocks (1.4 bpg). He was ACC Player of the Year. He was the Wooden Award winner as national player of the year.

“That’s the difference with him, his competitive nature,” Bilas said. “He’s not the type of player, I think, who’s going to lead the league in scoring, but he does so many things well and he’s such a competitor. He’s on the upper tier, I would say, of athletes I’ve scouted over the years. … He doesn’t go into a game thinking, well I’m going to score 25 in this one. He just makes the right play, then he stacks the right play over and over, and at the end of the game he’s got 20-something points and 12 rebounds and seven assists and a couple blocks, a couple steals. He’s productive because he makes the right play over and over again.”

A big brother’s job is to take a little brother down a peg or two if necessary. Make sure the head doesn’t get too big. Hunter Flagg said he hasn’t needed to perform those duties.

“He doesn’t need anybody to keep him humble. He stays grounded. He’s one of the most humble, hard-working kids I know,” he said.

Bilas said Flagg compares favorably to some of the top players picked over the last 20 years. And he won’t turn 19 until late December. He’s got a lot of growth yet to come, Bilas said.

Will there be adjustments? Of course. Will the NBA overwhelm Flagg? Of course not.

“For anybody, it doesn’t matter if you’re 18 or 22 coming into the league, it’s more physical. Players are bigger, faster, stronger. So it will be an adjustment, but it was an adjustment from high school to college, and he made it in no time. So I don’t doubt he’s going to do really well,” Bilas said.

The draft will be on ABC and ESPN at 8 p.m. Wednesday. Expect big ratings in Maine.