THE NAB AFL free agency period opens on Friday but it could get off to a slow start.

Richmond tall Tyrone Vickery's expected move to Hawthorn is a chance to be confirmed on Friday, but rival offers for Fremantle forward Chris Mayne and North Melbourne midfielder Daniel Wells are unlikely to be lodged.

Mayne is understood to have been offered a four-year deal worth more than $500,000 a season to join Collingwood, but some of the finer points in that deal still have to be resolved.

Wells is expected to join Collingwood on a three-year deal worth up to $600,000 a season, but his manager, Liam Pickering, has said he won't be making an announcement on his future until after North's best and fairest count on Friday night.

Adelaide defender Ricky Henderson is also likely to find a new home, but his move is unlikely to be confirmed until later in the free agency period.

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St Kilda remains on the lookout for a key defender but, contrary to reports, won't be pursuing Greater Western Sydney's Aidan Corr, who is a contracted and a required player at the Giants.

Saints chief operating officer Ameet Bains told NAB AFL Trade Radio on Thursday the club was "having all types of conversations about bolstering our key defenders".

St Kilda was interested in Giants key defender Caleb Marchbank, but 2014's No.6 draft pick has nominated Carlton as his preferred club.

However, the Saints' defence will again be able to rely on Sean Dempster in 2017, with the 191cm veteran signing a new one-year deal, taking him off the free agency list.

The Saints also have fellow veteran Sam Fisher ready to play on if they don't land a tall defender.

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Nathan Brown, Mitch Brown and Kaiden Brand are among this year's out-of-contract key defenders, while Eric Mackenzie could also be tempted from West Coast for the right offer.

North Melbourne is still believed to be interested in Nathan Brown, but it's understood the Roos' plan to trade for the Collingwood defender rather than acquire him as a free agent.

Wells' expected departure to Collingwood will likely net North an end-of-first-round or second-round free agency compensation pick, but the Roos would risk having that pick downgraded if they recruited a free agent.

The Brisbane Lions are also looking to bolster their backline and their CEO, Greg Swann, confirmed on Thursday they will try to broker a trade for Jack Frost with Collingwood.

But Swann said the Lions had cooled on Melbourne defender Lynden Dunn.

The Lions' CEO also said the club would consider parting with pick No.2 in this year's draft if offered the right deal.

Earlier on Thursday, Essendon list manager Adrian Dodoro told NAB AFL Trade Radio the Bombers had received inquiries from several clubs interested in trading for the No.1 pick.

Greater Western Sydney is one club that has approached Essendon, with Sandringham Dragon Andy McGrath believed to be in the Giants' sights if they can prize the first pick from the Bombers.

Richmond has been linked with out-of-contract Sydney Swans ruckman Toby Nankervis, who is understood to have interest from at least one other Victorian club and another club from outside Victoria.

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The Tasmanian, who played 12 games for the Swans, remains a required player at this year's runners-up but will assess his options over the weekend.

The future of Tigers midfielder Brett Deledio remains clouded with industry sources believing odds are diminishing that he will be at Richmond next year.

The Swans are awaiting a decision from Tom Mitchell and a resolution of the collective bargaining negotiations to determine how much flexibility they have in what they can offer their out of contract players.

If the 23-year-old decides to join Hawthorn, he will add to the juggling act required of Hawks list manager Graham Wright to trade in Gold Coast's Jaeger O'Meara.

AFL.com.au understands contracted forward Luke Breust will be at the Hawks next season, while other options thrown forward such as James Sicily and Billy Hartung are not likely to be attractive to the Suns.

Hamish Hartlett looks to have thrown Port Adelaide a curveball ahead of next week's trade period with his announcement he wants to play on at Alberton in 2017.

The Power are focused on trading players for draft picks this trade period as they seek to regenerate the list that has missed the past two finals series after looking poised for sustained success following their 2014 preliminary final appearance.

Hartlett loomed as the central piece in that strategy given he had the star quality to tempt rival clubs to part with an early draft pick or picks.

The Port vice-captain also still has five years to run on a lucrative deal at Alberton and trading him would have allowed the Power to get that money – or most of it – out of their salary cap, giving them greater flexibility with their list management over the next few seasons.

It seemed a foregone conclusion Hartlett would move after Port told him he was on the trade table following an underwhelming 2016 season where he finished 17th in the club's best and fairest count.

That sense grew stronger when Hartlett met with several Melbourne clubs including Essendon on Tuesday. But just two days later the midfielder performed a stunning about-face, saying through his manager, Michael Doughty of TLA, that he wanted to stay at Port.

Although not categorically ruling out a trade, Doughty said it was now "highly unlikely". He also said Port was comfortable with his client's decision.

That might be true but the Power will now have to scramble to bring in the extra draft picks they were banking on.

Ruckman Matthew Lobbe is still pursuing a trade to a club where he can be No.1 ruckman, but rival interest in him is only preliminary at this stage.

Contracted defender Matthew Broadbent is unlikely to move after his manager, Tom Petroro of Stride Sports, said on Wednesday he had received no opposition inquiries about his client and doubted he would shift clubs.

So the Power might have to look at trading other high-profile players if they are still committed to investing heavily in this year's draft.