Training Gianna Bryant, Mamba Sports Academy team left lasting impression on local instructor Zac Boster

CRYSTAL LAKE – With his back to the basket, Ryan Sroka gave a quick fake left toward the lane, spun right toward the baseline and rose for a fadeaway midrange jump shot. 

Zac Boster grabbed the rebound and demonstrated the move in slow motion, describing each motion in detail. 

“Don’t even show it baseline,” Boster said, indicating a slight fake Sroka had been doing with the ball.

Boster took a hard dribble, then turned his hips so his back was to the basket. 

“This is already selling it,” Boster said. “So you don’t need to show it again.” 

He handed the ball back to Sroka, who practiced the move again: Back to basket, one dribble left, spin right, fadeaway jumper. The shot was off the mark, but the execution was better. 

Bouncing basketballs from eight or nine players drowned out all other sounds in the gym on a Sunday afternoon at Harvest Bible Chapel in Crystal Lake. Boster walked to the next basket, watching other players work on their moves. 

Sroka, while his partner worked on the fadeaway, stood on the sideline, replicating the move, his eyes glazed over – in his own world. 

Boster, 29, of Huntley, has spent his adult life training basketball players. He works full time as a private instructor. He has coached everyone from local youth players to Carmelo Anthony and other NBA talents. There have been countless influences on his basketball coaching style. It started almost as a hobby, working with high school and youth players for free when he was in college. He worked with Pure Sweat Basketball in Crystal Lake. He moved to New Mexico to coach a junior college. In 2018, he went to California, not sure what was next.

Opportunity found him. While in California, he received a text from a coaching friend: “Hey, would you have any interest in working with the seventh grade girls team that Kobe Bryant coaches?” 

Uh, yeah, Boster thought. 

Boster knew it would be a unique opportunity, but he didn’t realize how much his days at Mamba Sports Academy in Thousand Oaks, California, would influence his coaching philosophy. 

“I’ve been fortunate to spend a lot of time around high-level coaches, but I’ll be honest, what I took away from Kobe has impacted me as much as any of these high-major coaches or professional coaches that I’ve spent time around,” Boster said. “He wanted these girls to have the ability to have an imagination and create on their own.”

Boster wants his athletes to have that same creativity. 

Sroka imitated the fadeaway again. Fake left, spin right, fadeaway jumper – Kobe Bryant’s signature move. 

From across the gym, over the din of bouncing basketballs and squeaking shoes, Boster’s voice rose. 

“Sroka, that was it right there. That was perfect.” 


This month has been difficult for the basketball community after the death of Kobe Bryant, 41, Gianna Bryant, 13, and seven others in a helicopter crash in Calabasas, California, on Jan. 26. The public memorial for Kobe and Gianna Bryant is Monday at the Staples Center in Los Angeles. 

“It’s been hard to see all this stuff, but I think it’s therapeutic to hear all the stories and see how many people loved Kobe, Gigi and everyone who was on the helicopter,” Boster said. 

Boster wanted to be clear: This story is not about him. It’s about the nine people who died in a helicopter crash on a foggy Sunday morning outside of Los Angeles. 

That text in 2018 was from Alex Bazzell. Boster was staying in Playa Vista in Los Angeles. Boster and Bazzell previously worked together through Pure Sweat. 

Bazzell trained his then-girlfriend, now fiancé, Napheesa Collier, who was a standout women’s basketball player at Connecticut and earned the WNBA Rookie of the Year award in 2019 with the Minnesota Lynx. 

Kobe and Gianna were fans of Collier. At some point, they asked Collier if they could watch her train. She invited them to a session with Bazzell. 

So later, when Gianna and her teammates told Kobe they wanted to take their game to the next level, Bryant called Bazzell. Bazzell knew he would need help, so he reached out to Boster. 

Days later, Bazzell and Boster drove to Sports Academy in Thousand Oaks (it wasn’t yet rebranded as Mamba Sports Academy) for three days of training. The girls said they wanted to commit themselves to the game, and the weekend was designed to be a test. Bryant wanted to see if they were up for what that would entail. 

He wanted three, two-hour practice sessions each day, with other activities in between – yoga, weight training, mental training. Bazzell and Boster were in charge of the 6 hours the girls spent on the court each day. 

“He was just throwing everything at them,” Boster said. “At first I was like, ‘Of course Kobe wants to do that.’ I didn’t know him at the time, but that just sounds like Kobe.”

That morning, he met Bryant and the girls, including Gianna, Alyssa Altobelli and Payton Chester, all of whom died in the crash. He met Christina Mauser, who coached the team with Bryant and also died in the crash. Mauser ignored Boster’s attempt at a handshake and greeted him with a hug. Boster soon realized that was just who Mauser was. 

They went to work teaching the girls high-level footwork. That first weekend in 2018, the girls struggled in the drills, but Boster could see the potential. 

Boster had heard countless stories about Bryant’s intensity as a player. He was expecting the five-time NBA champion to be the same as a coach. 

“He’s going to be really controlling,” Boster said. “He’s going to want to have his hand in everything – and it couldn’t have been any different.”

Bryant allowed Bazzell and Boster to do their thing. Bryant sat on the sideline and simply watched. As he worked with Bryant and the Mambas a dozen or so times over the next year, Boster came to see that Bryant’s laid back demeanor as a coach was intentional. 

“He wasn’t about giving them answers all the time, even though he had all the answers,” Boster said. “He realized and understood that if these girls wanted to make it to the highest level, he wasn’t going to be with them in the moment when they miss a shot and they have to figure out what they’re going to do next.

“He wanted to put them in positions to use their imaginations and create.”

Bryant likened it to a painter: A great painter doesn’t need to be told what to paint, he just needs to know how to hold the brush. Bryant wanted to teach the girls to hold the brush. Boster has tried to take that to heart with the players he trains in McHenry County and beyond. 

Boster’s favorite memory of that first day was after the workout, when he was leaving the gym. He hadn’t talked a lot that day, and he wouldn’t have been surprised if Bryant had forgotten his name. 

Instead, Bryant said, “Hey Zac, we’ll see you tomorrow.” 


Cary-Grove’s Beau Frericks passed the ball to Hampshire’s Kelby Bannerman beyond the 3-point line, then closed out with his hand held high. Bannerman gave a shot fake, one sideways dribble and rose for a 3-pointer. 

Sunday at Harvest Bible Chapel in Crystal Lake, time to get some work in. Sundays are the only day high school players have away from their teams during the season, and eight or nine varsity players were in the gym. All were boys, except for Bannerman, a junior for the Whip-Purs with multiple Division I college offers. 

One voice rose above the din. 

“Come on, Kelby. Quicker.” 

Boster took the ball from Bannerman. 

“Push the ball out,” Boster said, demonstrating the sideways dribble. “Side step. Pop.” 

Frericks threw another pass to Bannerman and closed out hard and fast. Push. Side step. Pop. Bannerman missed the shot, frustration mounting on her face. 

Bannerman started working out with Boster in eighth grade. 

“I would come in three, four times a week every summer, and we wouldn’t move on from a skill until I had mastered it and I’m able to use it in a game multiple times,” Bannerman said.

Bannerman moved to the top of the key, still working on the side dribble. Push. Side step. Pop. This one splashed through the net.

Minutes later, Wauconda native Matt Mooney walked through the door carrying two regulation NBA basketballs. Mooney was a guard on Texas Tech’s 2018-19 team that reached the NCAA championship game, losing to Virginia in overtime. 

He now plays on a two-way contract for the Cleveland Cavaliers and the NBA G League’s Canton Charge. Mooney has been coming to Boster for three or four years.

When Bannerman, Frericks, Sroka and the others finished, Boster spent some time 1-on-1 with Mooney. Boster had watched a lot of film of Mooney and believed Mooney could improve his 3-point shooting off the dribble. 

So that’s what they worked on for the next hour. It was the All-Star break, and Mooney had a few days away from his team. 

“He was the best player development guy that I had ever worked with,” Mooney said of Boster. “He does a lot of game-like reps, game-like situations.”

Some of the high school players stuck around, sneaking photos of the pro basketball player working out in their gym. 

“That’s a strength of his,” Mooney said. “He can work with anybody. See where they’re at and work with them where they’re at.”


Boster was lucky enough to work with the Bryants, meet the Altobellis and share hugs with Mauser. Their passion for the game lives on in the way Boster teaches young men and women to approach the game.

When Boster learned about the crash, he was – where else? – in the gym. 

It was another Sunday at Harvest Bible Chapel. Boster had finished with a younger group of players and was ready for the varsity players at 2 p.m. 

Boster noticed some of the guys huddled around whispering. Sroka asked Boster if he had heard about Bryant. LeBron James passed Bryant on the career scoring list the night before. 

“You mean like LeBron passing him or whatever?” Boster said. 

Sroka said no, Bryant passed away. Boster didn’t want to believe it at first. 

“You better go check your phone,” Sroka said. 

Knowing Bryant, Boster believes he would’ve been disappointed that Boster couldn’t find it in him to lead the workout that day. Boster left the gym for a while. Sroka and Frericks led the workout. 

“He was too torn to really do anything, which is understandable,” Frericks said. “I’d been going to him for so long, so I know the workouts.”

Sroka grew up a huge Bryant fan. He had a Bryant binder growing up. He still has a Bryant T-shirt. 

“It didn’t even feel right to play while Kobe wasn’t here,” Sroka said. “It was really quiet the whole time. Nobody was talking or smiling or anything.”

They took initiative of their own development, just as Bryant would have wanted. 


Boster left California after his first weekend with Bryant and the team because he had already accepted a job as an assistant coach at New Mexico Junior College in Hobbs, New Mexico, and it was time to go. 

Months later, in spring 2019, he returned to California for pre-draft workouts. He connected with Bazzell again and trained the Mamba Sports Academy team a few more times last spring and summer. Before Boster returned to California, Bazzell told him he was going to be shocked by how much the girls had improved. 

And he was. 

“It just makes me sad that I won’t be able to see those three girls grow up,” Boster said.

He worked with the Mamba girls eight to 10 more times last year. In addition, he watched a handful of their games. 

Boster spoke with Bazzell a few days after the accident. Boster thanked him for sharing those experiences with him. 

Bazzell wrote an emotional tribute to Bryant days after the accident on his personal website.

“As I sit here crying about what life without you will be,” Bazzell wrote. “I can’t help but think about all the lessons you taught me from up close and afar. I’ve been given the impossible task of coaching the mambacitas in their first practice back. … I have to be strong for 8 little girls because your greatness and dedication to them demands that.”

Boster returned to McHenry County before the season and went to work with the local players. 

“That’s when he started preaching to us about ownership, getting shots up outside of here,” Sroka said. “Just being a man, getting here on time, simple things Kobe would say. It’s not even just moves and stuff like that, it’s simple stuff.”

Sroka still has some work to do on that fadeaway shot, but he’ll keep tinkering with it. 

“The fadeaway took me 50 minutes to even somewhat get down,” Sroka said. “He expects you to at least make sure you’re improving on it. It’s confusing. I would be lying if I said it was easy.”

Boster isn’t sure if he will work with the Mamba Sports Academy team again. He plans to return to California for pre-draft workouts, so hopefully he will get to see the girls then. 

The time he spent with Bryant and the Mambas helped him understand just how much he loves days like those Sundays at Harvest Bible Chapel. 

“I’m fired up about the opportunity to work with youth players, more so than probably ever,” Boster said. “I love working with NBA players and high-level college guys, but I’ve really – recently, after this happened – taken a lot of joy in being able to teach and put kids in positions to figure things out themselves.”

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