Tim Duncan and coach Gregg Popovich reflect on Duncan's career, from being the No. 1 overall pick in the 1997 NBA draft to winning five titles with San Antonio. (2:21)

LAS VEGAS -- Gregg Popovich is probably never going to get over basketball without Tim Duncan.

"There's a big hole in my belly," Popovich said of Duncan, the future Hall of Famer he coached for his entire 19-year career in San Antonio, who retired last week.

"I think about the culture and his humor. I've been used to that for 20 years and now it's gone. I have to find that in some other way, some other power, some other player. I have to do something. But life goes on for all of us."

This week, life without Duncan begins in earnest as Popovich coaches the Select Team at USA Basketball's training camp in Las Vegas. It's a way to get to know some of the players he'll likely be coaching when he succeeds Mike Krzyzewski as head coach of Team USA after these Summer Olympics. But it's also become an exciting challenge in the august of Popovich's own Hall of Fame career.

"I guess I can never stop, I can never retire," Gregg Popovich joked about his coaching future with both the Spurs and Team USA. Jason Miller/Getty Images

It was always believed Popovich, 67, would retire at the same time Duncan walked away. Now he's committed to coaching the San Antonio Spurs and Team USA for at least the next four years.

"You know what happened? I just got roped in," Popovich joked. "I had to keep making promises. Manu [Ginobili] was going to sign a few years back and he was like, 'Are you going to be here?' Tony [Parker], then Kawhi [Leonard]. Then when we were recruiting LaMarcus [Aldridge], he was like, 'Are you going to be here?' it just goes on and on. So I guess I can never stop, I can never retire.

"There's gotta be some time when we're trying to sign a free agent and he goes, 'Pop, are you going to be here?' and I say, 'Nope, I'm leaving next week.'"

While letting go of Duncan last week was incredibly emotional, Popovich said it's been good for him to work with the younger team at this camp.

"It's really fun. When you look at the group, it's almost like men and boys," he said. "I look at the Olympic team and then I look at the Select Team, and they're so young and thin, their faces look like they're little kids. I think about that, but then I think 10 of the 12 Olympians went through that program. It's a pipeline, it's a culture. These guys will be the same thing."

Krzyzewski compared the succession process with himself and Popovich to platoon leaders succeeding each other in the military.

"The fact that we're both military guys we understand that I have the unit right now and he's going to take command of the unit and we both want the unit to do well," said Krzyzewski, who coached at West Point and served as a field artillery liaison in South Korea. "We understand that. We've been good friends but this has been great for me and I think for him too; just for us to bond even more."

Popovich played basketball at the Air Force Academy, served five years of active duty and returned as an assistant coach for the Air Force Academy.

"Two academy guys following each other," Popovich said. "I don't think it's a requirement for the job by any means. But it worked out that way.

"I'm totally surprised and shocked when Jerry Colangelo called me because there's a whole lot of younger guys that could do the job. So I was thrilled. When you think about being able to be with these guys and represent your country, you say yes. You don't say, 'I'll think about it, I'll get back to you.' You say yes.

"In some ways, I'm scared to death. I gotta fill some pretty big shoes. This program has been pretty great for a decade after it was a debacle before. I feel that. I'd be lying if I didn't say I feel that pressure. I'm going to bust my butt and get it right. I'm going to squeeze all the information I can out of Coach K and Jerry [Colangelo] and everybody who has been here. Thank heavens Jerry's still going to be with the program. I'm sure Coach K will too. So I'm in good shape that way. I have all kinds of people I can lean on."