The AFL is set to classify Cale Hooker as an unrestricted free agent, making it harder for Essendon to retain him.
It was assumed Hooker would be a restricted free agent at the end of this season.
But the AFL website reported on Wednesday that he would have unrestricted status.
He is among 12 current Bombers under doping suspensions, meaning he will not play this year.
Earlier this week, it was reported Fremantle were preparing a massive five-year offer for the WA native.
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If Hooker is a restricted free agent, Essendon could match any offer from a rival club.
Then the only way he could potentially leave the Bombers would be through a trade.
But unrestricted free agency means Essendon are powerless if Carlisle decides to accept an offer.
If the AFL classifies Hooker as an unrestricted free agent, it means he is not in the top 25 per cent earners this year among Essendon players.
Hooker has become one of the league's top defenders, making the All-Australian team two years ago and last season winning the club best-and-fairest award.
