Dwane Casey does not like throwing things out.

It drives his wife Brenda crazy, but helps keep the head coach of the Toronto Raptors gainfully employed.

Nearly 30 years ago, while an assistant at the University of Kentucky, Casey began keeping files on opposing NCAA coaches. He still had them, plus a whole lot more, about a decade later.

That’s when Nate McMillan noticed the bulging files. McMillan was finishing out his playing career in Seattle and eventually joined Casey on Paul Westphal’s staff.

The standout player had never seen anything like it.

“One thing that was really impressive about (Casey) was he was a real student of the game,” McMillan told the Toronto Sun earlier this fall in Indianapolis, where he is now associate head coach.

“He had notebooks on every coach that coached a game and their plays and their calls. He had this envelope, this folder that he kept all of the plays on. He even put coaches that were fired and came back into the league two, three four years later. He would go to his garage, get out his folder, because they were pretty much running the same plays and their calls were pretty much the same. For everyone. He knew every play, every call each team was running,” McMillan said, smiling at the memory.

McMillan remembered that each Sonics assistant was responsible for preparing scouting reports, rotating every three games.

“Most coaches were preparing for your team, your next game, well, Casey (his friends, including Raptors general manager Masai Ujiri call him that) not only prepared for his next game, but he prepared for your next game too. So if you were sick or didn’t show up, he would have the scouting report,” McMillan said.

“When I became an assistant, he was a guy that I really watched as far as his preparation for the game. He was so well-prepared for each and every game.”

That has not changed. Not now that Casey has a three-year contract extension with the Raptors and job security for the first time, and probably not ever.

Casey said there was a method to his madness, and it wasn’t just about learning how to stop opponents. He was searching for things he could borrow in order to get better as a coach.

He was thinking down the line by seeing what greats like Bobby Knight, Hubie and Larry Brown, Phil Jackson, Larry Bird and the rest were up to.

“You go back and you may steal one drill or one play that happened years ago and it still works,” Casey said on Monday.

“You always use the information and try to incorporate it in what you’re doing. I’m always afraid to throw anything away, I keep all my notebooks, my wife is on me about throwing stuff away, I won’t let her do it. You never know.”

The idea of scanning everything and putting it on a computer is broached. Casey thinks about it. It could be a win-win for everyone, including his wife.

For now, though, he still goes to his garage, even when he is supposed to be on his down time, to see if his memory can be jogged. To see if there is something in those yellowing, fading notes that can help him improve.

“In the summer time, I go through a lot of old folders just to read, it’s like reading a book,” Casey said.

“You see some things that guys have used in the past. It’s funny how a lot of coaches have not changed. They (just) have different terminologies.”

Casey has changed, though, since his time in Seattle, since the raw deal he got in Minnesota, where he was fired with a .500 record just half-way into his second year at the helm.

“You grow every year as far as knowing the players. Every year I work to get better as a coach.

“Controlling the game, substitutions, how to handle timeouts ... All those things.”

And then, smiling wryly, he adds one of the absolute truths in sports: “I do know this: The better players you have, the better a coach you are.”

For Ujiri, it was an easy call to keep Casey around, even though he was Bryan Colangelo’s hire and new general managers tend to bring aboard their own choices.

“He’s such a humble guy, very easy to work with,” Ujiri said.

“That being said, we have our moments when you have to (have) tough conversations ... but I think coach knew some of the things he needed to get better at, we all know there are things that we need to get better at and he works so hard at them.

“He has a philosophy and I love that, defensive coach, and he’s growing in all the other areas and for me it’s phenomenal to see. I’m trying to grow with all I do too and it’s always great to have such a great partnership.”

Don’t expect Casey to change now that he has stability here in Toronto.

“I’ve never worried about job security, because I’ve worked my butt off. I’ve worked hard whether I’m in the last year of a contract, first year of a contract, you’re going to get the same thing.”

Casey has many friends around the NBA. Rick Carlisle, who he combined with to help lead Dallas to a title and Mavericks owner Mark Cuban strongly recommended him to the Raptors and his old friend McMillan is thrilled about how things have turned out for Casey in Toronto.

“He went about it the right way,” McMillan said.

“Minnesota when he was there, they weren’t patient enough with him or with the team and he really didn’t get the opportunity to coach. Up in Toronto, they have given him a chance and he’s shown that he could be one of the top coaches in this league. He understands the game, has a great feel for it, great communicator. He’s getting the opportunity in Toronto.”

And running with it.