Mills played a crucial role in the Spurs' 104-87 win against the Miami Heat, lifting the Spurs to a dominant 4-1 series triumph and achieving his childhood dream of winning the NBA title.

It was a massive moment for the former Canberra Cannons ballboy, scoring 17 points in 17 minutes and lifting the Spurs to a third-quarter lead.

But Heal, who played with the Spurs in 2003, predicted free agent Mills could earn the biggest payday of his career with contracts potentially worth up to $6 million.

Mills is at the end of a two-year $US1.113 million ($A1.2 million) deal with the Spurs, but his superb play-off efforts have put him firmly on the radar for rival clubs.

Mills, 25, faces the biggest decision of his career as he weighs up staying with the Spurs to chase more success, or moving to another franchise in pursuit of more court time.

"He's played his role with the Spurs, what he's done is opened the doors to earn a very big contract ... you'd have to be thinking in the vicinity of $5-$6 million a year and I think he's earned the right to test the market," Heal said.

"Whether that means he stays in San Antonio for more than what he's on or whether he gets rewarded by another team who view him as more than a role player and gives him a chance to start ... it's in his court and he gets to choose.

"He should be rewarded for what he's done, he's done his time and earned the right to get paid."

The 25-year-old could have had a career in the AFL with the Sydney Swans trying to recruit him before he joined the AIS basketball program.

But Mills opted for basketball, and after a successful college career with St Mary's and two Olympic Games, Mills now has his dream NBA title.

His NBA career has previously been halted by frustrating injuries and contract issues out of his hands, but Mills has come of age and cemented his place as a genuine contributor.

Mills credits Spurs greats Tony Parker, Tim Duncan and Manu Ginobili with fast-tracking his development.

His fifth season in the NBA was easily the best of his career and he transformed from bench-warmer to fan favourite with his lightning speed and ability to score.

His third-quarter scoring spree in the championship match helped lift the Spurs to the title.

Mills and teammate Aron Baynes join Australian legends Luc Longley (Chicago Bulls) and Andrew Gaze (Spurs) as the country's only four NBA title winners.

Mills is the first indigenous Australian to win an NBA championship.

Longley won three titles with the Michael Jordan-led Bulls while Gaze is regarded as one of Australia's greatest athletes.

"Patty has to be right at the top in any discussion of any Australian basketballer in the history of the game," Heal said.

"Luc winning championships with the Bulls was so significant, but Patty has put himself in the conversation with Luc and separated from everyone else."

Mills hoped he and Baynes' winning form could transfer to the national team as the Australian Boomers aim for their first medal at a major tournament at the world championships in Spain in August.

Mills hired a personal chef in the off-season and cut out guilty pleasures such as strawberry milk, cheese, Vegemite sandwiches and pasta to get him in the best shape of his career.

"Patty stepped up in crunchtime, I'm also just happy for basketball in Australia," Heal said.

"With Patty, Baynes [Cleveland guard Matthew Dellavedova] and a heap of European players, there's so much talent and that's the key. There's no doubt this is our best chance to win a medal."