Roberton, 21, has been recruited to help up St Kilda's stocks of taller defenders, an area the Saints were unable to redress during the trade period when they sought to acquire Mitch Brown from West Coast.

He was signed at the expense of third-year player Nick Winmar, who was sacked with a year to run on his contract, much to the disappointment the AFL Players Association and his management. Winmar's only chance of continuing his career, having missed last week's national draft, is via the preseason or rookie draft.

Roberton, who is 191 centimetres, managed 10 games for the Dockers this year, for a career tally of 37 over three years. Roberton's move to the Saints will be a homecoming of sorts, given he played junior footy at a local club in Frankston, near St Kilda's Seaford base. Roberton has been training with the Saints.

Another former Docker, Nick Lower, is training with the Western Bulldogs, who could also snare him as a delisted free agent.

The Dockers had indicated they would redraft Lower, but as a delisted player he can cross to the club of his choice without having to go through the draft (the pre-season or rookie draft in this case). Lower, 25, would become a three club player if he joins the Dogs, having started at Port Adelaide.

St Kilda's signing of Roberton follows the signing as delisted free agents of former Geelong players Tom Gillies and Jonathan Simpkin, who signed with Melbourne and Hawthorn respectively.

While delisted players can join the club of their choice without passing through a draft, Collingwood will have to use the rookie draft to pick up its ruck recruit - and ruck coach - Ben Hudson, whom the club has recruited in a similar role to Greater Western Sydney's Dean Brogan, who doubled as a part-time coach and player for the Giants this year after returning from retirement.

The Pies delisted Peter Yagmoor yesterday but could redraft him as a rookie as well.