In mid-December, between practices and games, Cal’s most recognizable freshman wrote a 20-page paper for a graduate-level course.

The assignment was complex: Weave class readings into a narrative on how institutionalized sports impact America’s education system. Jaylen Brown pulled from his own experience as a blue-chip basketball recruit. He argued that society pushes athletically inclined children toward sports, often at the expense of their intellectual development.

“The stuff I learned in that class I’ll probably take with me for the rest of my life,” Brown said.

When Cal fans look at Brown, they see a 6-foot-7 forward whose acrobatic dunks regularly appear on “SportsCenter.” They see the Pac-12 Freshman of the Year, projected to be a top-five pick in June’s NBA draft.

What they don’t see is the deep-thinking introvert who, ahead of the Pac-12 tournament in Las Vegas this week, is still warming to the spotlight.

Brown’s mother, Mechalle, calls her son “Old Man” because the 19-year-old talks much slower than his contemporaries. Typically a vegetarian, he eats meat on road trips only because he doesn’t want special treatment from the Bears’ support staff. Martin Luther King Jr. quotes dot his Twitter feed.

On free Saturday afternoons, Brown challenges old-timers to chess at a Bohemian cafe in Berkeley. Some of his closest friends at Cal aren’t athletes. All season, Brown has declined one-on-one interview requests.

“It’s not just that he wants to be an excellent basketball player,” said Derek Van Rheenen, the professor teaching Brown’s graduate-level course. “He wants to be a scholar.”

A beautiful mind

On a Friday evening in the fall, Mohamed Muqtar was running on the treadmill at Cal’s student recreation facility when he saw Brown dribble a basketball into a nearby gym. Muqtar, the Bears’ assistant director for student services, finished his workout to find a puzzling sight. The five-star recruit was trading jumpers on a crowded court with two female students in street clothes.

“Someday,” Muqtar told Brown, “you guys will have your own practice facility.”

“I’ve seen all that stuff,” Brown said, rebounding for his friends. “I came here for something different.”

Long before he was a McDonald’s All-American, Brown learned to not let his physical gifts define him. His mother helped foster his diverse interests.

In middle school, Brown was captain of the chess team. He was active in Habitat for Humanity and Men and Women of Distinction, another community service organization, at Wheeler High School in Marietta, Ga.

When all-star events took him abroad in recent years, Brown tried to learn the local language. He likes to meditate and practice hot yoga. When choosing between an FC Barcelona match or Atlanta Hawks game on TV, he clicks to his favorite La Liga team every time.

One day in 2012, then-Tennessee head coach Cuonzo Martin visited Wheeler to observe the powerhouse Wildcats’ 6 a.m. workouts. The rail-thin freshman pacing those drills caught Martin’s attention. “That’ll be our next big thing,” Wheeler head coach Doug Lipscomb remarked to him.

Brown took unofficial visits to Knoxville the next two summers. It struck Martin that, when talking to Brown, he noticed no hint of ego.

“He was just a nice kid,” Martin said. “You’d like to think they would all turn out to be that way, but I just thought he was a good person.”

Martin’s pursuit of Brown hardly waned after Cal hired him away from Knoxville in April 2014. But the Bears were fresh off a 10th-place Pac-12 finish and hadn’t challenged for a Final Four since 1960. It was college basketball’s elite — Kentucky, UCLA, Kansas, North Carolina and Michigan — that landed official visits from Brown last spring (NCAA rules limit recruits to five schools).

Everywhere he went, Brown felt something was missing. He weighed his options with Wheeler and Cal great Shareef Abdur-Rahim. The benefit of Berkeley, the former NBA All-Star told Brown, extends far beyond basketball.

In late March, Brown paid his own way to visit Cal. Muqtar, whose desk is next to the basketball office, walked Rivals.com’s No. 3 recruit in the nation around campus. Brown’s eyes widened when he heard about Cal’s distinction as the No. 1 public university in the world.

“In everything he’s trying to do, he wants to master it,” Bears associate head coach Tracy Webster said. “Everybody can play basketball, but he wants more than that.”

Learning curves

Last summer, when Brown approached Van Rheenen about enrolling in his course, the director of Cal’s athletic study center was reluctant. Never before had a freshman taken the class, which was part of a master’s degree program on Cultural Studies of Sport in Education.

Brown was persistent. So Van Rheenen told him that, if he received approval from the dean, Brown could take the course.

“I thought he would never do it,” Van Rheenen said. “Then there he was, first day of class. I don’t think he ever missed any classes, and he was a fully engaged member.”

Transitioning to Division I basketball was more difficult for Brown. For much of the nonconference schedule, he played out of control. Sitting extended stints with foul trouble made it difficult for him to find a groove. Even when he was on the court, his shot was inconsistent.

Martin used phrases like “learning curve” and “growing pains” to explain his prized recruit’s struggles. But Muqtar offered a more detailed theory. The worst stretch of Brown’s season was a four-game block in the first half of December, around finals time at Cal. He shot 13-of-43 from the field (30.2 percent), with 15 fouls and 10 turnovers.

Exams and papers, including that 20-page narrative for Van Rheenen’s class, wore on Brown. Come tipoff, he had difficulty concentrating.

“Berkeley requires a lot from you, so you definitely have to find a balance,” Brown said. “It definitely took me an adjustment phase.”

Added Muqtar: “Once finals were done and he could just focus on basketball, his game slowed down.”

In Pac-12 play, Brown averaged a team-high 15.9 points per game on 46.1 percent shooting. He consistently matched up against the opponent’s top scorer. When Tyrone Wallace missed five games with a hand injury, Brown doubled as the backup point guard.

NBA scouts have flocked to his games. Though he will avoid draft chatter until the season ends, Brown could have trouble justifying another year in Berkeley. DraftExpress.com projects him to be taken third overall, a spot that would come with nearly $12 million guaranteed based on the NBA’s current three-year rookie salary scale, not to mention potential endorsement deals.

Twenty years ago, another deep-thinking introvert from Marietta faced a similar opportunity. Abdur-Rahim left Cal after becoming the first freshman to win Pac-10 Player of the Year. The No. 3 overall pick in the 1996 draft averaged 18.1 points and 7.5 rebounds per game over a 12-year NBA career.

Then Abdur-Rahim returned to Berkeley, where he earned a sociology degree in 2012 with a 3.8 GPA. He runs a nonprofit organization in the Atlanta area and is working toward his MBA at USC.

“Shareef was in one of my (undergraduate) classes as a freshman,” Van Rheenen said. “Both he and Brown were mature beyond their years.”

Connor Letourneau is a San Francisco Chronicle staff writer. Email: cletourneau@sfchronicle.com Twitter: @Con_Chron

Pac-12 men’s tournament

When: Wednesday-Saturday

Where: Las Vegas

TV: Pac-12 Network & FS1