Cox attended the Power's 14-point win over Hawthorn at Adelaide Oval last Saturday night, having met with the club's players and football department.
After the win, coach Ken Hinkley joked he could do with Cox's height given the serious injury suffered by back-up ruck man Brent Renouf earlier that day.
The knee injury left Matthew Lobbe as the Power's only fit ruckman.
But the club's list manager Jason Cripps told portadelaidefc.com.au that while it was impressed by Cox's talent, the club's focus remained on developing its current international rookie, Irishman Daniel Flynn.
“I can confirm that we won’t pursue contract talks with Mason and his management team," Cripps said.
“We really like him and wish him all the best in the future but the reality is we already have an international player on our list in Daniel Flynn and we are keen to see this through and focus strongly on his development.
“From a list management perspective we saw Mason as being a long-term project rather than short-term fix for our ruck stocks.
“We will continue to explore the US Combine in the future and feel as though we got a good look at this time around which will keep us in good stead for future reference.”
Twitter: @AFL_Harry