Cadwallader, a 19-year-old small forward who plays for WAFL club East Perth, had been sounded out by a number of AFL clubs after earning selection in the WA state side earlier this year.
He returned a positive result from a random test taken during the state team program this year, with the A sample confirmed two weeks ago and the B sample confirmed late on Monday afternoon.
At this stage Cadwallader will not make submissions to the Australian Sports Anti-Doping Authority when it next meets on July 14, and if the positive test stands the WAFL will ban him from playing at any level for two years.
A clearly shattered Cadwallader, who has been stood down immediately, admitted doping and apologised to his family, teammates and the East Perth Football Club.
“There is no excuse. I’ve made a huge mistake and I’m going to pay the price for that mistake,” he said on Monday night.
“I only hope that I can come back to the game in the future and make a positive contribution.”
East Perth coach Tony Micale said Cadwallader had made an error of judgement, but the club would do everything possible to help him return to football.
“Dean has been in the sights of most AFL clubs (and) he would almost certainly have been drafted this year,” Micale said.
“I think that’s the tragedy of this situation in that Dean didn’t need to do it in my opinion. Dean had the natural talent to achieve at the highest level without using drugs.
“With the ability he possesses and the attitude that he has towards attaining his dreams, I’ve got no doubt he’ll come back and achieve it.
“We’ll certainly give him that opportunity.”
East Perth general manager Alex Wilson said the club supported the WAFL’s anti-drug position and did not condone the use of “performance-enhancing or any other drugs”.
“Dean will pay a heavy price for the mistake he has made but, to the extent permitted, we will support Dean and his family in his efforts to resume his career at the appropriate time,” Wilson said.
Cadwallader made his league debut for East Perth in round two this season and had played every game up until the club was notified of the first positive result.
Nandrolone is used to build muscle mass and improve strength and durability.
In 2007, disgraced sprinter Marion Jones admitted using the banned substance. British Olympic gold medallist Linford Christie tested positive for nandrolone in 1999.
