Toronto Raptors president Masai Ujiri says he's been able to repair his relationship with former head coach Dwane Casey, but doing the same with former Raptor DeMar DeRozan hasn't proved as successful.

Ujiri fired Casey after the 2018 season and traded DeRozan two months later to land Kawhi Leonard from the San Antonio Spurs. 

"It's not easy," Ujiri told TNT's Ernie Johnson of the moves in an interview posted on the NBA's Twitter account Monday. "If you have that human part of you, you feel it in your heart.

"I will never forget, I will never, ever forget having to do that with Coach Casey and walking to his office, waking up that morning. Many times I wanted to move it and change it or think that you're not making the right decision. It was incredibly hard, because Casey is an incredible person, and so great to work with. ... DeMar, I was in the hotel in Kenya, and I walked around that hotel at 4 a.m., 5 a.m., for a couple hours, trying to gather up enough strength and courage to make this phone call. I will never forget it.

"With Casey, it has gotten so much better now with his family and him. With DeMar there is still plenty of work to be done. But, by the grace of God, it will all get better. We have to continue to make these decisions that are tough. But that's the business of basketball, and the position that we are in."

Ujiri made the two major changes to the franchise after the Raptors were swept in the Eastern Conference semifinals by LeBron James' Cleveland Cavaliers for the second straight year. Casey was named NBA's Coach of the Year in 2018 after being relieved of his duties. DeRozan, who had led the team in points in each of the past six seasons, said he was blindsided by the trade in 2018.

The gamble would pay off for Ujiri, though, as Leonard starred during the Raptors playoff run in 2019 under head coach Nick Nurse, leading the team to its first NBA championship. Leonard, who was named Finals MVP, then left the team as a free agent to join the Los Angeles Clippers. 

"I always say that the two hardest things in our world, in our business, is trading a player and then when a player leaves, if a player leaves in free agency," Ujiri said Monday. "And it's hard on both sides. When a player is traded, it is hard on the player side, and when a player leaves, like us [with Leonard last summer], it is hard on that side. I've experienced all of it, from wonderful people.

"It sometimes puts a strain on relationships, as we saw with DeMar. People don't know even with [when we traded] Rudy Gay, I was close to Rudy. Incredible kid. Incredible kid with DeMar, where you build and you're trying to preach a culture of good, of trust, of being with people, and then you have to make this decision [to trade him].

"With Kawhi, we just built a relationship where we trusted each other, and that friendship has evolved even bigger after he left, and I'm proud of that. I support him with everything he does as a human being, and his family, and you move on. You've got to move on to the next ..."

When the NBA season paused in March, the Raptors sat second in the Eastern Conference with a 46-18 record, and Nurse praised the team's younger players on Monday for filling the void left by Leonard this season.

"Everybody's kinda taken a step forward and I think a lot of that has come about just because of opportunity," Nurse told TSN's Kate Beirness. "I think the first two guys I saw the next day after Kawhi said he was going to the Clippers were Fred [VanVleet] and Pascal [Siakam] and I said, 'Hey, about 30 shots a game just opened up,' and they both...said 'We're ready.' I think the spreading around of those shots and the improvement of Pascal and Norman [Powell], who looks so great this year, and Freddie. Those guys came back to camp as totally different guys this year and I actually like watching this team play from an offensive standpoint this year. We seem to have more options and more guys that can do it and were not kinda just trying to throw it to one guy to initiate so much."

The Raptors had clinched a playoff berth prior to the season being suspended, reaching the postseason for the seventh straight year.