SAN FRANCISCO – Ten years ago, Derrick White’s lone college basketball offer was a preferred walk-on, partial scholarship to a rebuilding Division II program. The only other option was a junior college in Wyoming. There was no star ranking next to his name as an ignored high school recruit in Colorado.

But Thursday night, the Boston Celtics guard continued to write his motivational story by scoring 21 points off the bench during a stunning 120-108 victory over the Golden State Warriors in Game 1 of the NBA Finals.

“Just don’t give up. Keep going. Keep working,” White said. “Enjoy what you do. I love basketball. So, I kept doing it. Good things started happening for me. So, do what you do.”

White was a 6-foot, 155-pound guard who averaged about 20 points during the 2011-12 season as a senior at Legend High School in a Denver suburb. Longtime trainer and mentor Marcus Mason said that he and White’s parents sent about 50 highlight DVDs of White’s senior season in high school to college basketball programs on all levels. The common denominator from those that did respond was that he was too small.

Mason was stunned that college coaches were missing White’s potential.

“I remember calling at least 50 to 60 coaches that I knew, had a good relationship with, and every guy said: ‘Marcus, you got to be crazy. This guy’s not a college basketball player,’ ” Mason said. “And so, we sent letters, we sent videos with his mom and dad, and we just couldn’t get anybody to bite. He never passed the eye test.”

Initially, the only four-year offer was a non-scholarship one from then-coach Jeff Culver at NAIA school Johnson & Wales, best known for its renowned culinary arts program. Culver kept in mind that White was only 17 years old when he graduated, and his father was tall, so there was potential for a major growth spurt.

“You could tell he was getting used to the body growing. But he was out there making winning plays. And his basketball IQ stood out, decent enough handles, decent enough shot, was competing out there. And just a guard that looked like he could maybe play a couple different positions,” Culver said. “It piqued our interest. And we’re typically looking at under-the-radar kids as much as we can, and in Colorado, a state that the basketball level isn’t that high, kids will often get overlooked when you do get some decent players coming through.”

But after Culver left Johnson & Wales to take the head-coaching job at Division II University of Colorado Colorado Springs, he offered White a $3,000 scholarship as a preferred walk-on with an opportunity to earn a full scholarship as a sophomore. Although tuition was about $20,000, White bet on himself, got a student loan and took the best opportunity he had.

“When I took my visit, I was just thankful that Coach wanted me,” said White, who paid off his college student loans once he got to the NBA. “I hadn’t been to the Springs much until then. So, just seeing the Pikes Peak and the beautiful scenery they had on that campus was a cool and good fit for me. There was no chance at that time that I was going to make the NBA. I was trying to play overseas. It’s pretty crazy.”

Said Culver: “They saw an opportunity to get their foot in the door at a D-II and bet on himself, right? And he knew, and we had told him that the money would grow, especially after that first year, if he earned it and he did. But they were willing to take that chance on the first year.”

Culver was a little surprised to hear that White dominated a pro-am league in Denver in 2012. White arrived in Colorado Springs, 4 inches taller and getting stronger. His roommate was fellow freshman Alex Welsh, who was on a full scholarship.

White was supposed to be redshirted as a freshman and didn’t play his first three games.

“He was basically a practice player,” said Welsh, who plans to attend NBA Finals games in Boston. “It started to get really weird because he was killing everybody on the practice squad. He’s giving all the starters work. Nobody can guard him. He’s doing stuff. He’s surprising people every day. It’d be weird because we’d go home, and he’d be the redshirt guy.

“The scholarship thing is funny now, but in the moment, it wasn’t something that was openly talked about. At the time, I knew that he probably wasn’t on scholarship, or he was on a little bit of scholarship.”

After several UCCS players suffered early injuries, Culver decided not to redshirt White, who averaged 16.9 points as a freshman and was named the 2013 Rocky Mountain Athletic Conference Freshman of the Year.

“I grew a little bit. I started working a little harder. I put some muscle on, and it started working. Everything started to come together at once,” White said.

By the time White was a junior, he was a Division II superstar averaging 25.8 points, 7.4 rebounds, 5.2 assists and 2.1 blocks. Now 6-foot-4 and much stronger, the two-time first-team All-RMAC selection scored 50 points against Colorado School of Mines and led the Mountain Lions to the 2015 NCAA Division II men’s basketball tournament. White also landed NCAA Division II All-American honors in 2014 and 2015.

White suddenly went from unknown to an NBA prospect as teams started coming to his games to scout him.

“Our junior year, even when he scored 51 in a game, and he does this, he does that, and it’s effortless for him, it was never really clicking in my head that the NBA was an option,” Welsh said. “What was happening our junior year when he was really, really, really good, I was like, ‘He’s going to transfer.’ That was the next step that I was thinking.”

Said Culver: “I thought maybe we’d lose [White] after the first or second year, to be honest with you. I know he had a lot of people sniffing, especially after his second year. And then after his third year, I thought actually we might be in the clear. We had been in conversations with probably about a half-dozen NBA executives at that time. People knew about him. He was on the radar. We felt good about being able to line him up with an agent, get him in the workouts and all that stuff.”

The humble and mild-mannered White avoided discussing the elephant in the room until he surprised Culver and Welsh with some big news one day. White told them he had decided to transfer to the University of Colorado in 2015.

“I felt bad for him because he was really nervous to have that conversation with me,” Culver said. “And it was tough for him, but told me he was looking at transferring and going to CU. So, it was a little bit of a shock at first. And then I’m just thankful it worked out.”

Welsh, who currently lives in Denver and works in tech sales, said, “He’s a shy guy now, but he was even more shy back then. So, I’m like, ‘This is weird.’ And he comes in, I’m sitting at this desk I got in my room, and he sits down on my bed. He’s so nervous. He’s being so quiet, and I’m like, ‘What’s up bro?’ And I could feel the writing on the wall, like, ‘OK, he’s about to go. He’s about to transfer. He is about to tell me he’s leaving.’ And he’s like, ‘I’m transferring.’ I was like, ‘To where?’ And he’s like, ‘CU.’ And I remember saying, ‘I’m so happy for you.’ ”

White believed that transferring was necessary to give him his “best chance to make the NBA.”

“I wanted to challenge myself at the highest level in the Pac-12 playing for my home state school,” White said. “I wanted to challenge myself.”

“Every day he’s done something new to make you go, ‘That’s why he’s here.’ ”

White had to use his available redshirt during the 2015-16 season due to the NCAA transfer rules with the Buffaloes. Sitting out allowed him to adjust slowly to the Division I game in practices and the weight room. Culver believes that redshirt year was key for White.

Once White was eligible, he didn’t disappoint, averaging 18.1 points, 4.4 assists and 4.1 rebounds during his senior season while also being named to the 2017 All-Pac-12 first team. Being invited to the 2017 NBA combine solidified White as a real NBA prospect.

“I was in Europe playing in Poland,” Welsh said. “So, I’d get up at 3 a.m. or to watch his game. And it started to click. I’m like, ‘Yeah, he’s definitely not coming over here. I think that he’s going to the NBA.’ ”

The San Antonio Spurs selected White with the 29th pick in the 2017 NBA draft. White played 17 games as a rookie under Hall of Fame head coach Gregg Popovich. He would grow into a solid role player for the Spurs, averaging 13.2 points, 4.2 assists and 3.3 rebounds from 2019 to 2022.

On Feb. 10, White was traded from the Spurs to the Celtics for Josh Richardson, Romeo Langford, a 2022 first-round draft pick and a 2028 first-round pick swap. White averaged 11.0 points, 3.5 assists and 3.3 rebounds primarily as a reserve in 26 regular-season games with Boston.

Celtics guard Marcus Smart first became familiar with White during USA Basketball training camp last year. Smart was a gold medalist for the 2020 U.S. Olympic basketball team and White played for the development squad that they practiced against. Smart believed that White would be a great fit for the Celtics upon arrival.

“Derrick, he played for a great organization,” Smart said. “He played under a great coach. We knew that Derrick understood the game, the way he plays. Watching him play before we got to USA reminded me a little bit of myself. So just instantly off the bat, I loved the way he played. Coming into that when we would practice, he was never backing down, no matter what.

“When you got a guy like that, and me, a guy like Derrick, it’s always going to be some battles. But it’s nothing but respect there. That’s what it’s kind of been showing. Every day he’s done something new to make you go, ‘That’s why he’s here.’ ”

In Game 1 of the NBA Finals, White continued to show why he is here as he scored 21 points and nailed five 3-pointers, including two in Boston’s frantic fourth-quarter rally, becoming the first Celtics reserve to score 20 points in the championship series since Leon Powe in Game 2 of the 2008 NBA Finals.

White told Andscape after the game that he felt great but shifted the attention to the team, saying it was just one win. Mason, who still mentors White, responded by saying, “Never get too high. Never get too low.” White nodded.

“He’s a role model to me for all young kids and young people out there because he does it the right way. And he’s a guy that people like, not just the basketball side of Derrick White, but he’s a likable guy and very good person,” said Mason, who attended Game 1.

Ten years after the basketball world had no idea who he was, the world is watching White in the NBA Finals.

“To see him thrive in his role, but then to also be able to taste the success with the team along the way, it’s just been sweet to watch and be a part of,” Culver said.