An out-of-contract Bomber has requested a trade away from Essendon this off-season, following weeks of movement speculation.

Key-position defender Brandon Zerk-Thatcher, who remains without a contract for next season, has requested a trade to Port Adelaide.

Zerk-Thatcher hails from South Australia, with the 25-year-old having previously played football for Sturt.

A Round 4 draft choice in 2017, the flexible backman has developed into a solid starting option for Brad Scott's defence. However, the Bombers missed out on September action this year as their back six struggled mightily throughout the final games of the season.

Along with the Power, the Adelaide Crows were understood to be interested in making a play for Zerk-Thatcher, though it appears Port has ultimately won him over.

The Bomber joins fellow key defender Esava Ratugolea in requesting a trade to the Alberton club, with the versatile Cat making his intentions clear last week.

Port Adelaide is also understood to be interested in acquiring little-used Melbourne ruckman Brodie Grundy, who also calls South Australia home.

As Zerk-Thatcher cannot exercise free agency rights this year, Essendon and Port Adelaide will need to strike a trade agreement once the exchange window opens on October 9.