FREMANTLE has done the deal to see James Aish become a Docker.

The Dockers gave up a future second-round selection (on-traded from St Kilda) and a future fourth-round selection (on-traded from St Kilda) to Collingwood to land the backman.

In return, Fremantle received Aish plus pick No.69 and a future third-round selection.

Aish has agreed to a three-year deal with Freo.

It means the South Australian has joined his third club, after he was drafted by Brisbane at pick No.7 in 2013.

Aish had been contracted at Collingwood for 2020 but his relationship with Justin Longmuir, who was the Magpies' defensive coach before being appointed to the senior role at the Dockers, meant there was a strong lure for the 23-year-old to head west.

"James was identified for his outside run as well as his ability to play at half-back," Fremantle list manager Mark Micallef said.

"We feel that his ball use and his competitiveness are also big assets he can bring to our football club.

"James said that Justin Longmuir, who coached him during his time at Collingwood, was a big drawcard to his coming over to Fremantle.

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"We feel like we’ve got someone who can be a part of Fremantle’s future for a long period of time."

He had been seeking an extension with the Pies but the club wasn't in a position to do so, as it prepares for deals to keep Brodie Grundy, Jordan De Goey, Darcy Moore and Scott Pendlebury, all of whom will enter the final season of their respective deals next year.

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The Pies will expect Tom Langdon to come into their backline after missing a bulk of the campaign with a right knee injury that eventually required surgery.

Aish has lined up in 82 games throughout his career.