Melbourne midfielder Brock McLean has dropped an AFL trade bombshell, with the potential Demons captain set to join Carlton.

The Demons and Blues have reached an in-principle agreement that the 23-year-old will join Carlton in return for their first-round draft pick, at No.11.

Melbourne are resigned to losing McLean and it is the first confirmed transfer in the lead-up to next month's trade week.

While McLean is out of contract, it is still a massive surprise that the deal is effectively done.

He was barely on the radar in the last few weeks as the media speculated about potential trade deals.

Only five months ago, McLean said he would like to succeed James McDonald as Melbourne captain.

McLean was dumped from the Melbourne leadership group before the 2008 season for doing a burnout in a car park at a training session.

But he said in May that he was turning his career around.

"I think I'm heading in the right direction," McLean had said.

"If I'm the right person for the job whenever Junior (McDonald) steps down or decides that he doesn't want it, then I'd love to do it."

In August last year, McLean stunned and delighted the club when he put in $10,000 of his own money for their first "Debt Demolition" campaign.

He played 19 games this season for a career total of 94.

While there is speculation about the playing future of Carlton onballer Nick Stevens, it is understood the main reason the Blues targeted McLean is they wanted a "grunt" midfielder who could give more support to captain Chris Judd.

McLean met with the Demons on Monday morning to confirm he wanted to leave.

"It is very disappointing to lose a player of Brock's calibre," Demons official Tim Harrington said in a club statement.

"Once Brock made this decision it was important that we secured a commensurate trade - this has been achieved."

The Demons pointed out the trade meant they would now have four picks in the top 18 at the national draft.

But McLean's departure will rob the young Demons list of vital experience and talent.

Melbourne have finished bottom for the last two seasons and will have a priority pick in the draft.

McLean said the decision to leave the Demons was hard.

"I have come to the decision that the best thing for my football career is to move on from Melbourne," he said.

"While it has been an extremely tough decision as I have given the club my all, I am confident it is the right one for both parties."

Carlton declined to comment on Wednesday night, with the trade not confirmed until after a medical screening and the necessary paperwork.

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