FREMANTLE defender Brennan Cox has rejected the temptation of testing the free agency market, signing a bumper six-year contract that all but guarantees he will end his career as a Docker. 

Cox, 25, was due to become eligible for free agency at the end of his next contract in 2024, but he will now be a Docker for the next seven seasons. 

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Key defenders are hot property in this year's player movement period, with Ben McKay (free agency), Esava Ratugolea and Brandon Zerk-Thatcher among the talls on the move. 

Cox was drafted to Fremantle in 2016 at pick No.41 and has established himself as a key part of Justin Longmuir's side in defence, playing alongside fellow 2016 recruit Luke Ryan. 

He has played 102 games in seven seasons in the west and finished ninth in the club's best and fairest behind winner Caleb Serong. 

Cox's new contract means he now has the longest guaranteed tenure at the club, ahead of fellow key talls Luke Jackson and Jye Amiss (both contracted to 2029) and Serong and Ryan (2027).