Gregg Popovich overjoyed that Derrick White finally believes

As his old coach looks on, Derrick White celebrates a fourth-quarter basket Sunday at TD Garden.Jim Davis/Globe Staff

Derrick White was walking toward the TD Garden court to take warm-up shots Sunday when a Spurs public relations staffer spotted the Celtics guard and asked if he wanted to make a quick pit stop first.

“Do you want to see Pop?” White was asked.

White smiled and nodded. Moments later, a door swung open and he headed in to greet his former Spurs coach, Gregg Popovich.

Popovich and the Spurs drafted White 29th overall in 2017, and the guard spent his first 4½ NBA seasons in San Antonio before being traded to the Celtics last year.

“Derrick’s a really special case of someone over time figuring out that he belongs, basically,” Popovich said before White had 19 points in Boston’s 137-93 rout.

White appeared in just 17 games as a rookie before starting 55 his second year. Popovich said he displayed an unusual work ethic and willingness to learn.

“You could see he had the size at that position to do it, and the immediate thing you could see was he had an instinctive nose for the game,” Popovich said. “He understood how to play. Most NBA players don’t know how to play. He did. He added skill development on top of that.”

Still, Popovich said, White sometimes allowed self-doubt to creep in. He tried to make White understand that he was not out of his league.

“Repetition is important,” Popovich said. “Making him believe that you really believe what you are saying to him, showing him a lot of love. The coaching staff did the same thing. At that point, it’s up to him and that will come with any success that he would have.”

With his team getting blown out late in the fourth quarter Sunday, Popovich enjoys a laugh with Blake Griffin.Jim Davis/Globe Staff

This season, White has thrived for Boston. He entered Sunday night’s game averaging 12.3 points, 4 assists, and 3.5 rebounds per contest. The Celtics have outscored opponents by 9.9 points per 100 possessions with him on the floor, the best net rating on the team, and were a plus-41 with him on court Sunday.

Pop hoping for the best with Ime Udoka

Former Celtics coach Ime Udoka played for the Spurs under Popovich for three seasons before spending seven as his assistant. Udoka led the Celtics to the Finals last year in his first year as a head coach, but this year he was suspended before being fired for having an improper relationship with a subordinate team employee. “Ime was and is and always will be a great friend,” Popovich said. “You can imagine that I was deeply disappointed and hurt for him, for everybody involved. It’s a difficult situation for him and my hope is that he will bounce back and find a home” . . . Celtics forward Jayson Tatum missed Sunday’s game due to a left hip contusion. It likely will be just a one-game absence. Point guard Payton Pritchard sat out his ninth game in a row because of left heel pain, and guard Malcolm Brogdon had 20 points and nine assists in 26 minutes after missing one game with lower back pain.