ESSENDON and Hawthorn will be unable to offload their first-round draft picks in trade deals this year unless they can obtain a second prized selection. 

And West Coast will also be blocked from trading its 2021 future first-round pick unless it can acquire an early choice this year.

WHO'S MOVING? All the latest trade and contract news

Under the AFL's future trading rules clubs must use two first-round picks at the NAB AFL Draft over a rolling four-year period to ensure they aren't able to swap selections and trade themselves into long-term list strife.

There is a clause in the rule that allows clubs to apply for permission to trade out their picks even if they haven't met the rolling two-in-four criteria. The AFL in that case would assess the quality and age of the players brought into the club for those first-round picks.

The Bombers haven't used a first-round pick since they selected Andrew McGrath with the No.1 overall choice in the 2016 intake, having traded out their first pick in 2017 in a deal for Devon Smith and their 2018 and 2019 first-round selections to land Dylan Shiel.

The Bombers entered round 17 sitting in 12th position, which would hand them pick No.6 (after Fremantle's adjusted pick due to its points deficit).

Hawthorn, too, has only used one first-round pick in the past four years, which was exciting youngster Will Day last year. The Hawks traded their first selection for 2017 as part of the deal to secure Jaeger O'Meara and then used their first pick in 2018 to recruit Chad Wingard from Port Adelaide.

DRAFT HUB Latest news, profiles, highlights, more

The clubs are headed for top picks at this year's NAB AFL Draft, with the Hawks currently holding pick No.3, which would be their earliest selection since 2005.

Tall forwards Logan McDonald and Riley Thilthorpe, key defender Denver Grainger-Barras and midfielder Elijah Hollands would be in the mix for the Hawks' pick if it remains in that spot.

The Hawks, however, can trade their 2021 first-round pick if they hold on to their 2020 top selection.

The clubs would be able to trade their respective first-round selections for different picks later in the first round. They could also deal them if they brought in any extra first-round picks as part of other trades or as free agency compensation.

For example, if Joe Daniher left Essendon as a restricted free agent and the Bombers received a first-round compensation pick for him, they would then be able to trade one of them.

The Bombers' interest in fellow restricted free agent Brad Crouch does create a fascinating backdrop to the upcoming free agency period, however, for if Essendon was to secure Crouch as a free agent that would rule out any compensation they would receive if Daniher was to depart. It would essentially be a straight swap.

Such a case happened in 2013, when Eddie Betts left Carlton and the Blues didn't receive a compensation pick under free agency rules because they had recruited Dale Thomas as a free agent.

The Eagles traded out their first-round picks in 2019 and 2020 last year to bring star midfielder Tim Kelly back to Western Australia, having used first-round picks in 2016-17 when the rolling period was underway.

Having now gone three seasons without a first-round pick, the Eagles will be barred from sending their 2021 first-round pick to any club in a trade deal.