Retiring: Carlton's Nick Duigan is leaving AFL football due to a knee injury.

Retiring: Carlton's Nick Duigan is leaving AFL football due to a knee injury. Photo: Sebastian Costanzo

Carlton has rejected suggestions it was ''blindsided'' by Nick Duigan's sudden decision to retire, insisting the club always knew his degenerative knee problem might not allow him to fulfil the final year of his contract.

Duigan officially announced his retirement from football on Monday, confirming a Fairfax Media report from last week that forecast a parting of company between the 29-year-old and the club he served for three seasons.

As his departure was not confirmed until after the national draft and end of the free-agency period, it was feared the Blues might be left one player short on its list for next season.

However, that situation has been averted, with Carlton revealing it had received permission to place Duigan on its long-term injury list.

The Blues are now free to elevate one of their rookie-listed players, possibly former Collingwood ruckman Cameron Wood, to whom coach Mick Malthouse threw a football lifeline to late last month.

Carlton football manager Andrew McKay said the club was aware of the full extent of Duigan's knee condition, but claimed it hoped to manage the issue throughout 2014.

''Unfortunately the doctors have now made it very clear that his knee will not cope with another year at AFL level,'' McKay said.

''To suggest that Nick has somehow let the club down by not reaching his decision earlier is simply inaccurate. At all times Nick has been entirely open and honest about the condition of his knee, and his ability to play on,'' he said.

The decision means Duigan's playing career ends on something of a high despite his playing only five games in 2013 after falling out of favour with Malthouse, where before that he was a regular in Brett Ratten's back line.

In his second last game, Duigan was the shock match-winner with four goals in Carlton's elimination final triumph over Richmond.

Duigan, a qualified psychologist, said the decision to not fight through another season was a difficult one.

''But it's certainly the right one for both myself and the club,'' he said.

''I want to thank Carlton for giving me the opportunity - it has been a fantastic club to be a part of.''