GREATER Western Sydney veteran and two-time All Australian Chad Cornes has announced his immediate retirement due to an ongoing knee injury.

The 33-year-old played 16 games in the GIANTS' inaugural season, but has been unable to make it onto the field this year.

He had knee surgery in January but an infection the following month ruled him out for the majority of the season.

Cornes had hoped to play in the latter part of the year, but the injury hasn't responded and he has now made the decision to hang up the boots.

A member of Port Adelaide's 2004 premiership team, he also finished third in the Brownlow Medal that year behind Mark Ricciuto and eventual winner Chris Judd.

He initially retired at the end of 2011, but was thrown a lifeline by the GIANTS, leading to a player/coach role with the AFL's newest club.

Cornes, who started his career as a forward before being shifted into defence in 2004, finishes with 255 games and 179 goals.

He admitted in an interview last month he knew the end was near.

"Last year for me was just a real bonus," he said.

"I got out there and got to play with a great young group of kids and got given the chance by GWS to extend my career.

"I've loved that side of it and now it's time to do something else and move on to the coaching side of things.

"My knee's just not coming along as I would hope.

"It's a shame, but I'm putting my focus in to try to help out with the coaching and help these young kids, which I'm really enjoying."

Cornes played in GWS' first game and was also a part of its two wins last year, against Gold Coast and his old side.

The GIANTS' general manager of football Graeme Allan paid tribute to Cornes for his outstanding career.

"Chad has been a fantastic asset for the GIANTS both on and off the field," Allan said.

"He proved last year he still had good football left in him and with his leadership showed our young players what it takes to succeed at AFL level.

"Unfortunately he has not been able to get on the field this year because of a knee injury and we have badly missed his experience in our backline

"But he has continued to make an important contribution with his coaching role and we look forward to him continuing to help develop our playing group and congratulate him on a fantastic career."