Zerk-Thatcher is yet to confirm his future at Tullamarine beyond this year, with a call on where he plans to play in 2024 to come shortly after the Bombers' season reached its cessation on Friday night with a 70-point defeat to Collingwood.
While Zerk-Thatcher has been a reliable asset for senior coach Brad Scott this year - playing 22 matches in the red sash - Essendon are seen to be on the lookout to add height to their backline this coming off-season.
Port Adelaide is understood to also be keen on adding Ratugolea this trade period, having rekindled their interest in the forward-turned-defender after a failed move last year.
Ratugolea has gained reported interest from Hawthorn as well as the Bombers and Power, three clubs who have also been linked to McKay as the market for key defenders reaches an all-time high.
Essendon's interest in bolstering its backline comes as Zerk-Thatcher weighs up his future, with the South Australian now seen likely to lodge a trade request and return to his home state via a move to Alberton.
According to Fox Footy's Jon Ralph, Essendon are of the belief that Zerk-Thatcher, who turned 25 on Friday, will depart the club this year.
Outgoing Bombers football boss Josh Mahoney told Ralph a contract has been on the table for Zerk-Thatcher for some time, however the club understands he'll look to assess his options elsewhere.
"He has had a deal in front of him for a long period of time," Mahoney said, via Fox Footy.
"We would like to think he would stay, but we also understand he might be looking for another opportunity."
Essendon will also be awaiting contract calls from star midfielder and free agent Darcy Parish and fringe ruckman Nick Bryan in the coming weeks, with both players having garnered external interest from rivals this year.
Essendon could be prepared to get on the front foot come the player movement space, with their coach speaking on the need to "improve our list" after their shock Round 24 performance against the Magpies.
Scott said he looks forward to lifting expectations around the club as he enters his first full off-season window with the Bombers since he took on the senior coaching job, noting improvements are needed "right across the board".
"We need to improve our list, we need to improve our football department, we need to improve right across the board," Scott told media post-game.
"The recency bias is real. In a perverse way, the players leave with a sick feeling in their stomach and that should drive their off-season.
"This is the first opportunity I've got to drive an off-season. Not even a pre-season, an off-season, as to what that looks like and the expectations we have.
"The observations of the last 9-12 months is that it's nowhere near where it needs to be. We'll get that right.
"... now,the hard decisions become easier. What that means in terms of list management, it's too early to tell. Wer'e certainly in a very, very strong position in terms of list management to improve our list."
Essendon are in line to carry a top 10 selection into this year's National Draft after a poor finish to their campaign saw their finals hopes dashed in the final two weeks of the year.