Why the Celtics traded for Derrick White and Daniel Theis

Derrick White (right) tries to get past the Grizzlies' Ja Morant during a December game. Brad Stevens coached White at the World Cup in 2019.Nikki Boertman/Associated Press

In the summer of 2019, Brad Stevens was serving as an assistant with USA Basketball when he went to Las Vegas to help the team prepare for the World Cup.

That squad included Celtics Jayson Tatum, Jaylen Brown, and Marcus Smart. But Spurs guard Derrick White, a member of the USA Select team that was brought in to scrimmage against the main squad, truly caught the eye of Stevens, who was then the Celtics coach and is now their director of basketball operations.

“We’ve thought for years that Derrick was a really good fit with our best players,” Stevens said Friday. “He is an excellent defender. He just makes the right play on offense over and over and over.

“He’s a guy that only cares about winning, that will do all of the little things, as you can see in some of his stats, defensively, with regard to willingness to put his body on the line, activity, shot challenges, all of those things.”

White was promoted to the World Cup team in 2019, joining Tatum, Brown, and Smart. And on Thursday he was reunited with the Celtics’ top trio when they acquired him from San Antonio in exchange for Josh Richardson, Romeo Langford, and a 2022 first-round pick. In addition, the Spurs will have the option of swapping first-round picks with the Celtics in 2028.

The Celtics also brought back center Daniel Theis, acquiring him from the Rockets, and sending Dennis Schröder, Enes Freedom, and Bruno Fernando to Houston.

Celtics coach Ime Udoka was an assistant with San Antonio during White’s first two seasons there and he said the guard, who played for Division 2 Colorado-Colorado Springs before transferring to Colorado as a senior, made a real impact on the Spurs during the predraft process before being selected in the first round in 2017.

“He was a well-rounded player right off the top, and a guy that due to age and playing four years in college was mature already coming in to contribute on a veteran team,” Udoka said. “So he checks a lot of boxes across the board — offensively, defensively, as a person, as a player. He’s someone we’re obviously happy to have.”

During his 15-minute interview session Friday morning, Stevens stressed numerous times that his approach on deadline day was based on the desire to add players who will accentuate the skills of the Celtics’ thriving starting lineup for the long term, particularly Tatum and Brown. Both White and Theis are under contract through the 2024-25 season.

“The most important thing is that this is not just about the next three months with [White],” Stevens said. “this is about, again, adding guys that you think and can see playing in a seven-game knockdown, drag-out playoff series and you know they can be on the floor and play a role in helping you win.

“And, obviously, [White and Theis] do that very differently, but both of those guys can do that and they both can do that for years to come.”

White arrived in Boston Friday morning and Theis is expected soon, but as of Friday night, the Celtics were still waiting on all of the players in the deals to have their physicals completed.

Daniel Theis (right) and Jayson Tatum will be reunited.Matthew J Lee/Globe staff

While White was one of the Celtics’ primary targets entering Thursday, the return of Theis, who spent 3⅓ seasons with the Celtics before being traded to the Bulls in a salary-clearing move last year, came together in the rushed final minutes before the 3 p.m. deadline.

The starting frontcourt of Al Horford and Robert Williams has been quite effective, but both players have dealt with nagging injuries during their careers, and Theis is an excellent insurance policy for both.

“Theis knows how to make our best players better,” Stevens said. “That’s the best thing he does is he has a great feel for making others around him better. He’s got a savvy for the game. And he can play a role.

“And so if Rob misses a stretch, Theis can plug in and, off the bench, with Grant [Williams], if we play minutes without Robert or Al on the floor, Theis can play the exact role that those guys are playing now and do so at a high level.”

The Celtics traded their 2021 first-round pick last year in the deal that sent point guard Kemba Walker to the Thunder, and now Stevens has surrendered another one in the White trade. It’s a clear departure from the approach of former president of basketball operations Danny Ainge, but Stevens said the desire to acquire White outweighed the need to keep another pick that figures to fall somewhere in the middle of the first round.

“First-round picks are really valuable, but getting a guy for 3½ years on a great contract that is a perfect fit next to your best players is valuable, too,” Stevens said, “and you’re just weighing that.”