MELBOURNE, AUSTRALIA - JUNE 01: James Aish of the Magpies marks the ball against Brandon Matera of the Dockers during the round 11 AFL match between the Collingwood Magpies and the Fremantle Dockers at Melbourne Cricket Ground on June 01, 2019 in Melbourne, Australia. (Photo by Michael Dodge/Getty Images)

Collingwood defender James Aish is one step closer to joining the Dockers, with the 23-year-old flying to Western Australia for a medical with Fremantle.

The Dockers have put a three-year deal in front of Aish according to his manager Liam Pickering, although Aish is still contracted through to the end of 2020.

"He's been approached by Fremantle to go and play there for three years," Pickering told SEN on Tuesday.

"Justin Longmuir, who's come from Collingwood, is desperately keen to get him there.

"We've been trying to extend him, and Collingwood have been pretty up front about it and said, 'Look, we wouldn't be able to do anything until potentially this time next year'.

"(Collingwood said), 'If there's somewhere else that you're going to be guaranteed to play and is going to be a good opportunity for you, we won't stand in your way'. And we know Longmuir loves him."

The Pies floated the idea past Aish over the last few days, with the No. 7 draft selection now contemplating his future at Collingwood.

Aish played in the Pies' grand final side last year, and was brought in for their preliminary final this year.

"It's up to him what he wants to do. He can stay at Collingwood and run the gauntlet (or leave for Fremantle)," Pickering said.

"He's had a few chats with Fremantle now. It's only happened over the weekend. It's his decision."

The defender has played 50 games for Collingwood since joining the club at the end of the 2015 season.