AFL premiers Melbourne have moved to shore up their midfield depth with the acquisition of St Kilda discard Luke Dunstan as an unrestricted free agent.

The Demons confirmed the move on Wednesday as the annual trade period kicked into gear, following a slow start.

Port Adelaide picked up key forward Jeremy Finlayson in exchange for a future third-round draft selection, while Geelong confirmed they are one of several clubs interested in former Richmond and Adelaide small forward Tyson Stengle.

The Crows warned they could attempt to use the AFL pre-season draft to secure sought-after wingman Jordan Dawson amid an ongoing trade battle with Sydney.

Melbourne had no such issues landing Dunstan, who was a first-round draft pick in 2013 and played 116 games for St Kilda but fell out of favour under Brett Ratten.

Despite that, he received 11 Brownlow Medal votes from his dozen games in 2021 and averaged 25 disposals per outing.

The tough 26-year-old will give the Demons' vaunted midfield group more support following the retirement of Nathan Jones and the departure of Aaron vandenBerg.

"We came into this trade period looking to re-stock the midfield area and Luke fits the bill perfectly," Melbourne list manager Tim Lamb said.

"We are really happy that Luke has chosen to make the move to our club.

"We think Luke's best football is ahead of him and just as importantly, Luke is a terrific cultural fit for our club."

Adelaide's negotiations with Sydney over Dawson could drag into next week, with the Crows unwilling to part with their first selection - No.4 overall - at the national draft.

Their next selection is not until No.33 after they were involved in a four-way swap of draft picks with Melbourne, St Kilda and the Western Bulldogs late on Wednesday.

The deal should help the beaten grand finalists secure father-son prospect Sam Darcy.

But the Crows will have to get creative if they are to satisfy the Swans, who offered Dawson a five-year contract and rate the skilful 24-year-old the best player on the trade market.

Earlier, Adelaide football director Mark Ricciuto said the pre-season draft could come into the picture if they cannot reach middle ground with Sydney before next Wednesday's deadline.

"It's certainly not the way clubs like to do deals - they like to reward the club that had the player," Ricciuto told Triple M Adelaide.

"But I guess at the end of the day if it (a trade) doesn't happen, I guess that's an alternative."