EAST LANSING, Mich. — Tom Izzo, the men’s basketball coach at Michigan State, was in his office sharing stories about Draymond Green. Stories about the practices when Green would get so angry that he would punt the ball off the ceiling. About the halftime speeches that Izzo never asked Green to deliver. About the clipboards that Izzo smashed and the games that Green helped win and the friendship they built.

“Even as he gets older,” Izzo said, “he’s never forgotten where he came from.”

Just then, as if on cue, Green’s hulking figure appeared in Izzo’s doorway. Green, a forward with the Golden State Warriors, was back on campus Tuesday to have his college number retired that night, and as he and Izzo hugged, Green complained about the cold weather.

“You’re getting soft, man!” Izzo said. “You look great. How are things?”

“I’m in and out of the lineup, but it’s O.K.,” Green said. “I’m only playing like 20 minutes a game. They’ve got me on a minutes restriction because of my heel. Trying to get that right.”

“You’re not turning into one of those ‘load management’ guys, are you?” Izzo asked.

“Nah,” said Green, who sounded almost sheepish about his modest workload.

Green told Izzo that he was heading over to the practice court for a workout, just like the old days. But he also had a big night ahead of him. The ceremony was scheduled for halftime of Michigan State’s game against Duke, and Green had requested a preposterous number of tickets for family and friends.

“I think he thought we were going to play this game at the football stadium,” Izzo said.

It was an emotional homecoming for Green, 29, who reminisced about growing up in nearby Saginaw with dreams of playing for Michigan State. The university changed him, transformed him, he said, his time there defined above all by his relationship with Izzo, whose primary mode of communication was tough love. Green described the coach as a friend and a father figure.

“You come in as a freshman, and you’re like, ‘Why is this guy so tough on me?’” Green recalled. “It’s like, ‘Can’t you settle down a little?’ But then you realize the reason he’s on you so tough: He always says: ‘I’m one of the few people in life that’s actually been able to live out their dream. I want the same thing for you.’”

About an hour after the Warriors’ 104-79 loss to the Hawks on Monday night, Green had boarded a private plane in Atlanta that was bound for Michigan. He was joined by his fiancée, their two children and a few friends from the Warriors, including Coach Steve Kerr, who sipped a beer, and D’Angelo Russell, a teammate who spent the first half of the flight studying game film on his laptop. Green uncorked a bottle of red wine and offered generous pours.

“You ever done a wine tour in Bordeaux?” he asked Kerr. “You’ve got to go.”

It has been an unusual season for the Warriors, who are injured, inexperienced and have the league’s worst record after five straight appearances in the N.B.A. Finals. The Michigan trip was a welcome reprieve for everyone involved, and Green was buzzing with anticipation by the time the plane landed at an airport a few miles from campus.

“Welcome to the great state of Michigan!” Green shouted as Russell rubbed the sleep from his eyes.

Since leaving Michigan State, Green has won three N.B.A. championships and an Olympic gold medal. He recently signed a $100 million contract extension. He vacations in France and spends his summers in Southern California. His fiancée, Hazel Renee, had a recurring role on the television show “Empire.” LeBron James has become one of his pals.

But back when Green enrolled at Michigan State, he was pudgy after spraining his ankle as a high school senior — “I called him my Pillsbury Dough Boy,” Izzo recalled — and played sparingly as a freshman. Sometimes, he did not play at all. After Green failed to shed his warm-ups during a win at Ohio State, he cried on the bus back to East Lansing.

“I’m not sure I even envisioned him starting,” Izzo said. “It was definitely a process, and he was kind of old school in that sense. He got better with his body, got better with his game, got better with his intelligence. He just kept getting better, which is part of what made it so rewarding.”

Izzo lamented how people these days seem to lack patience — not just in college basketball, but in every pursuit. Instant success. Quick rewards. Immediate results. Green was none of those things. His development was a slow build. He worked hard for four years and absorbed the lessons that the coaching staff offered him.

“You realized that this was a guy who probably wanted me to be successful more than I even wanted to be successful,” Green said of Izzo. “Like, as much as you say, ‘I want to do this,’ and, ‘I want to do that,’ very rarely are you going to do everything that it takes to get there without any guidance.”

“We both wear our emotions on our sleeves,” Izzo said. “You never went home wondering if he was mad or upset about something. I always knew.”

At the same time, Izzo said, Green seemed to savor campus life. He went to a rowing regatta and attended track meets. He watched baseball and soccer. He even donned pads as a tight end for a spring football game — he drew a penalty flag for a false start — and bundled up for his first hockey game, which he loved because a fight broke out.

“That was right up his alley,” Izzo said.

Part of Green’s lasting appeal with Michigan State fans has to do with his everyman nature, Izzo said. He has battled his waistline. His growth took time. Even now, he sometimes struggles to control his emotions. (And, yes, sometimes he doesn’t even try.)

His fiery nature has attracted the watchful eye of N.B.A. referees; he has five technical fouls in 14 games this season and has been ejected once.

“But everyone knows how passionate he is,” Izzo said, “and I think that’s one of the reasons why he’s so revered around here.”

And while Green has been critical of the N.C.A.A., arguing in support of recent legislation that would permit college athletes to reap financial benefits from the use of their names and likenesses, he has maintained strong ties to Michigan State. In 2015, he donated $3.1 million to the athletic department, part of which went to finance the construction of the Draymond Green Strength and Conditioning Center. The old weight room was a dump, Green said. When he saw the new one for the first time, he brought his son, Draymond Jr.

“I don’t see my name up there,” Green said. “I see my son’s name, and that means everything to me.”

After his workout and some business meetings on Tuesday, Green was feted at a cocktail reception before the game against Duke. He seemed anxious about his speech, which surprised family members.

“I’ve never seen him nervous about anything,” said his mother, Mary Babers-Green.

Another batch of Warriors officials arrived, fresh from the West Coast, including Joe Lacob, the team’s owner, and General Manager Bob Myers, who played for U.C.L.A. yet has never had his number retired — “No, it should be worn in perpetuity by anyone else,” he said — but understood the significance of the honor.

“I think it’s the immortality of it,” Myers said. “Not a lot is forever anymore, but that’s lasting, and it’s real.”

Warriors guard Klay Thompson, who is out injured, made the trip, too, and raised the roof when he saw Green. They are the last pieces of the Warriors’ championship core along with Stephen Curry, who could not attend because he was having surgery to remove pins from his fractured left hand.

“I’ve been through so many battles with this guy,” Thompson said of Green.

At halftime, Green made his way onto the court. He kept his speech short and sweet — 12 seconds shy of his four-minute limit, including a couple of pauses to choke back tears. Then, the banner with his name and his No. 23 went up to the rafters as the pep band played the Michigan State alma mater.

Izzo was back in the locker room, coaching his team for the second half.