Eligibility
Clubs receive selections in the draft based on where they finished on the AFL ladder during the year, for example, Melbourne finished last in the 2008 AFL season, therefore receiving the first pick in each of the three drafts (National, pre-season and rookie). Teams have the choice of whether to participate in the pre-season draft; many clubs fill their playing roster at the National Draft, and hence do not participate in the pre-season draft. Also, unlike the national draft, picks in the pre-season drafts cannot be traded between clubs.
Read more about this topic: AFL Pre-season Draft