Walt Williams, a former Maryland basketball and NBA star, now serves as an assistant coach for the Sherwood boys’ basketball team. His sons Tyrese (25) and Kamari, third from left, are on the Warriors this winter. (Katherine Frey/The Washington Post)

Walt Williams stood on the sideline with a lanyard around his neck and a yellow shirt over the broad shoulders of his 6-foot-8 frame. He watched as his middle son — No. 42, with the chicken legs — dribbled into the corner and stalled the possession. And then he shouted, unleashing his booming but soothing voice into the Sherwood High School gymnasium.

“Don’t just take off running,” Williams said. “Triple threat!”

To many, Williams was and remains a local legend, known for reviving the University of Maryland’s basketball program before playing in the NBA for 11 years. But nowadays, the 45-year-old father of three spends his afternoons at a high school gym in Sandy Spring. He is not just an ex-NBA player to the teenagers in the blue and white practice jerseys. He is a mentor. He is a voice of wisdom. He is “Coach Walt” — or, in a couple instances, “Dad.”

Williams is a third-year assistant under Tim Gilchrist, but he’s been around most of these players for the past decade, coaching them in youth leagues, running their basketball camps and even joining them for family vacations. Parents and children were starstruck when they first saw Williams coaching in the St. Peter’s Catholic Church Youth League in 2008, and some still are to this day.

But the Sherwood teenagers don’t see him as a celebrity. (Most of the players on the Warriors’ roster were in preschool when Williams played his last NBA game, in 2003.) They see him as a coach — one who just so happens to be very tall, very charismatic, very knowledgeable and very good at shooting three-pointers.

“I see him as a mentor now,” sophomore Davis Long said. “Basketball, it’s all about learning and experience. He’s always teaching us what we can do to improve our game, how to get better at it.”

Walt Williams was an all-American for Maryland after sticking with the Terps in the wake of a scandal that resulted in a coaching change. (James M. Thresher/James M. Thresher)

Williams played 11 years in the NBA with six franchises, including the Portland Trail Blazers in the 1998-99 season. (David Taylor/Getty Images)

Williams didn’t used to be a shooter. He didn’t used to be the tallest kid in the gym. As a freshman at Crossland High in Temple Hills, in fact, he was the waterboy — on junior varsity. He was 5-9, skinny and gangly, and had never played organized basketball. He suffered from asthma; according to his mother, Theresa Williams, his doctor wrote a note telling coaches to restrict his minutes.

But Walt Williams, who grew up playing pickup ball at Benjamin Stoddert in Prince George’s County, was always a competitor. His first high school game came midway through his freshman season. Most of the JV team had been ruled academically ineligible, and he ended up playing from start to finish. Apparently, to Theresa’s dismay, that note never made its way to Crossland’s coaches.

Still, Williams’s mother was proud. So was his father, the late Walter Ander Williams Sr. Thirty-one years later, Williams still remembers looking in the stands after the game and seeing his father staring back.

“It was a proud look, and I’d never seen that before,” Williams said. “That was my quest. I wanted to make him have that look every time.”

Williams sprouted 10 inches in high school, developing a big man’s body to go along with his point guard’s court vision. After a state title and two finals appearances at Crossland, he made his way to College Park. He stayed with the Terps amid a coaching change, turning down legendary North Carolina coach Dean Smith twice and eventually becoming an all-American. As legend has it, Walt Williams saved Maryland basketball.

He was selected seventh overall in the 1992 NBA draft, but tragedy struck a few months later when his father died of cancer at age 47. The death hit Williams, then 22, hard. The elder Williams used to go to nearly all of Walt’s games, shouting at the referees and cheering on his son. “It was a little bit embarrassing at first,” Walt Williams said. But he learned to appreciate it. A lot of his teammates’ fathers weren’t at their games, he said, but Williams Sr. always was, always giving “that look.” Until one day, he wasn’t.

Tyrese Williams and his younger brother Kamari go after a rebound at a recent Sherwood basketball practice while their father, Warriors assistant coach Walt Williams, looks on. (Katherine Frey/The Washington Post)

Walt Williams poses for a photograph with sons, Kamari, a Sherwood sophomore, left, and Tyrese, a senior, at the school. (Katherine Frey/The Washington Post)

After retiring from the NBA, Williams returned to Maryland, and he now lives in Brookeville with his wife, April — they were high school sweethearts — and his three kids: Tyrese (17), Kamari (15) and Bryce (11).

By day, he’s a financial adviser at Legacy Wealth Management Group, by night he’s a broadcaster for his alma mater, and on weekday afternoons, he’s a basketball coach — doubling as a dad — for one of Montgomery County’s top teams.

The players said it’s helpful having a former professional basketball player around. He brings a unique perspective as someone who has played against the world’s best athletes — and he doesn’t mind filling in when they’re a man short in drills and scrimmages.

“He’s really into it, he loves basketball, he loves giving back, and he loves coaching us,” senior Chris West said. “Like, he could be doing better things, bigger things right now, but he’s here, giving back to the community.”

It’s a different dynamic for the Williams brothers. Kamari is a raw but talented 6-5 sophomore guard who earned the nickname “headache” from his father, “because I had a big head when I was young.” He admits it can be embarrassing when his father calls him out during practice, but he proudly wears his father’s number on his practice jersey anyway (the No. 42 game jersey was too big).

Tyrese, a 6-2 senior guard who leads the team in scoring, said Walt’s yelling can be a little too much sometimes. If the Williams brothers have a bad practice, their father will let them hear it on the car ride home. But Tyrese takes pride in having his father and an NBA veteran on his sideline — booming voice and all.

“You learn a lot more when your dad is your coach,” Tyrese said.

You also learn a lot more when your coach is a retired NBA player, said Davis Long, whose youth teams were co-coached by Williams and his father, Tim Long.

Tim recalled one game several years ago when Walt made a halftime adjustment — switching to a 1-3-1 defense — that helped the team come back and beat a savvy Silver Spring team for the eighth-grade championship.

“He’s not just a great player,” Tim Long said. “He has this unique ability to see things that most people don’t see on the court, and I think that holds true today.”

That basketball IQ by itself would be an asset on most coaching staffs. Williams knows when to switch to a zone, how to set a screen and why it’s important to always be ready for the jump shot. But that’s all secondary when it comes to coaching, he said. After all, one of his most influential coaches — his father — never said anything about skills or strategy or technique.

“It was just about playing with toughness, playing with heart. It was those types of things that he really paid attention to,” Williams said. “That’s what I try to instill in my kids, and anyone that I coach.”