Mills also said on his first day of San Antonio Spurs training that the pain of missing out on a historic Olympic medal with the Australian Boomers will fuel his championship ambitions this year.

Mills is preparing for the biggest season of his career and returned to Spurs training on Wednesday to begin the final year of his contract with the franchise.

His individual form and team success will dictate the next move of his career and the size of the million-dollar offers that get thrown his way.

But the No.1 priority is getting back to the NBA championship series and making sure Duncan can be proud of the team he built in a phenomenal 19 seasons with the Spurs.

The Spurs won five championships during Duncan's career, including teaming up with Mills for the 2013-14 title.

"It's obviously different," Mills said of Duncan's absence.

"I think the onus is on the rest of the guys, that have been here for a while now, to be able to follow in his legacy that he's built here. He set the bar, the standard very high for us.

"For us to make him walk away from this very comfortably, it's to know that we've got this, and we can lead everyone else, and lead everyone in the right way and right path, to know that this is the Spurs culture, and this is what he had built for so long."

The Spurs' first season without Duncan since 1996 opens the door for players like Mills to take on more leadership duties.

Mills was a star performer for Australia at the Rio Olympics in August, but left Brazil heartbroken after the Boomers failed in their medal quest.

Mills won world-wide plaudits for the way he handled himself after the Boomers lost their bronze-medal match to Spain.

But the pain deep inside, coupled with an earlier-than-expected NBA play-offs exit last year, is driving Mills to make this year the best of his eight-year career.

"With the national team I'm a leader and a point guard ... with the Australian team it comes naturally," Mills said.

"This Spurs culture is heading in that direction with these newer and younger guys, we've got to get around them a bit more.

"The Spurs culture is all about team and togetherness ... this has to move forward together and not leave out any pieces.

"[The last NBA season] is something that still burns inside of me now ... knowing that we didn't bring it. It's been burning all summer.

"I put a bit of that fire into the Olympic campaign and now into this. They're all learning curves."

The Spurs begin their pre-season against the Phoenix Suns on Sunday (AEST) before beginning their regular-season campaign against the Golden State Warriors on October 26.