Carlton will part company with defender Nick Duigan, the player whose four goals helped the Blues overcome Richmond in a final, in a sudden decision that will leave the club one short on its senior list for 2014.

Duigan, who has a degenerative knee, has decided not to play in 2014 despite being contracted for next season. Unfortunately for the Blues, Duigan's departure did not happen before the national draft and end of the free-agency period, when another player could be added to the list. The club will seek to bring a rookie up to replace him and might place Duigan on the long-term injury list, even though he will be gone from the club.

Duigan and the AFL Players' Association have been in discussions about finalising his departure and a financial settlement. It is understood that Duigan's decision to pull the pin, with a year left on his contract, came after he returned from the post-season break and was based on his doubts about his knee. He also had been clearly out of favour with Carlton coach Mick Malthouse, who felt that Duigan was only at his best ''zoning off'' and wasn't nearly as effective playing man on man in defence, as the coach preferred.

Duigan did not leave with the players on their trip to Arizona. His exit is set to be announced by the club soon, perhaps as soon as today.

Sources said that Duigan had not returned from the break in peak condition, partly due to his knee and on the understanding that he could be finishing up.

Duigan, who is 29 and did not make his debut until he was 26, played only five senior games in the 2013 season after he was a regular under Brett Ratten. He played in round one and did not re-appear

until round 22. But he was brought into the 22 belatedly for the elimination final against the Tigers, before 95,000 and played a major part in Carlton's stirring come-from-behind victory. Usually a defender, he was played in the forward line and booted four goals in what would be his second-last game for the Blues.

While he was out of favour in selection, Duigan was viewed as a leader among the playing group and was in the team's leadership group in 2013. A cerebral player with broad-ranging interests, he is a qualified psychologist, with an interest in refugees and worked with a group called ''Head Space'' that deals with mental health issues.

Originally a Victorian, Duigan was drafted out of South Australian club Norwood in 2010 when he was a surprise choice. He and fellow defender Jeremy Laidler were casualties of the new coaching broom at Carlton this year.

The Blues have a senior list of 38, plus six rookies, with the experienced duo of Heath Scotland and Jaryd Cachia listed as nominated rookies - and do not have to be upgraded. The Blues also have another experienced rookie in ex-Magpie ruckman Cameron Wood.