“It was packed,” he said, his voice climbing, of the regular-season finale on Feb. 21. “The bleachers were filled up. The back bleachers were filled up. I’ve never played in front of a crowd like that.”

Brennan, Milton Academy’s 6-foot-10 junior center from Weston, tipped home the winning basket with just over four seconds left against rival Noble & Greenough School to give his team a 54-53 win, and the program’s first Independent School League championship, sending the gym into a frenzy.

He remembered the noise, then the rush of people from all four sides of the floor converging at midcourt, celebrating the unprecedented achievement with him and his teammates.

As Brennan tells the story, his winning tip-in was the result of being in the right place at right time.

“It’s all kind of a blur,” he said. “But the play broke down. When I did get the ball, I actually missed a layup. Somehow I was able to tip it in.”

In every sense, Brennan has been at the center of the best season in the Mustangs’ history (20-4 entering Friday’s NEPSAC Class A semifinals against Phillips Exeter Academy). Averaging 12 points, 9 rebounds, and 2-plus blocks per game, he’s both a reliable option on offense and a game-changer defensively.

Milton coach Lamar Reddicks  says that, at his position, Brennan is the most skilled player he has coached. And he admitted that Brennan may be the most skilled center he’ll ever coach.

High praise considering Reddicks had one of the best bigs in the region two seasons ago in 7-footer Dennis Clifford , now a sophomore captain at Boston College. He battled with then-freshman Brennan every day in practice, providing his younger counterpart a tutorial on what it takes to hold his ground against college-ready talent.

“Every day was a grind,” Brennan said with a smile, as a Boston College media guide with Clifford on the cover sat within reach.

“Honestly, I could not stop him. There wasn’t too much I could do. But, definitely, I got to work on playing behind him, playing in the post. It helped me a lot. Every time I did something wrong, he’d tell me, he’d help me out.”

Since then, Brennan has developed into a highly sought-after Division 1 prospect himself. He has scholarship offers from schools like the University of Massachusetts, Providence College, Maryland University, Purdue, Rutgers, Vanderbilt, and a handful of Ivy League schools.

At 210 pounds, he knows he still has work to do in the weight room, but his skill set is leaps and bounds ahead of most players his size.

His jump shot is easy and its range extends out to 3-point territory. A righty when it comes to some things (throwing) and a lefty when it comes to others (writing), he’s ambidextrous around the rim, able to finish strong with both hands. And when it comes to his passing and dribbling skills, he’s like a guard — with a wingspan most guards can only dream about.

“We do a lot of skill work on Mondays,” Reddicks said. “He’s about as good as anyone at anything that we do. Whether it’s guard stuff, or big man stuff, or shooting, he’s good at all of them. For a guy his size, it’s incredible.”

Talented as he is, Brennan is just his team’s third-leading scorer.

Milton’s roster features eight seniors this year, including the ISL Player of the Year in point guard Max Motroni , guard Ryan Rizzo  from Needham, and the team’s leading scorer, All-ISL selection Nick Pagliuca from Weston.

Pagliuca is headed to Duke University, where he hopes to join coach Mike Krzyzewski’s team as a walk on. Nick’s father, Steve , is part owner of the Boston Celtics, and the younger Pagliuca credits Kevin Garnett with giving him a short shooting lesson in the locker room at the NBA team’s Waltham practice facility that helped him hone his jump shot into one of the best in the ISL.

“KG was actually really intense, and he asked me, ‘What do you look at when you shoot?’

“He says he looks at the rungs’’ that hold the net to the rim, Pagliuca said. “Every single time. Basically he was just telling me to focus, focus no matter what you’re doing. It works for him because he hits shots with people’s hands in his face. . . Since then I’ve been able to really picture the ball going in when I shoot.”

Pagliuca, Brennan, and Rizzo have known each other since they were fifth-graders at the Meadowbrook School in Weston.