Carlton deny utility Nick Duigan has blindsided them with his shock decision to retire from the AFL.

The Blues confirmed on Monday that the 29-year-old, recruited to the Blues from Norwood, would quit because of a knee injury.

Carlton said they will put the mature-age recruit on their long-term injury list, paving the way for his retirement.

He returned to pre-season training last month and it quickly became apparent that Duigan’s persistent knee trouble would continue.

“This is not a situation that has taken us by surprise,” Blues football manager Andrew McKay said in a club statement.

“Nick has had an ongoing knee condition which both he and the club were hoping could be managed through 2014.

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

“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.”