Lance Whitnall has conceded defeat in his bid to overcome a debilitating knee injury, the ex-Carlton captain quitting AFL football.

Whitnall, discarded by the Blues last month amid concerns his troublesome knee would not stand up to another season, said a second medical opinion convinced him his career was finished.

The 28-year-old had been considering nominating for next month's pre-season draft in order to continue playing, though there had been little interest from other AFL clubs.

But his hopes of playing on were dashed after a poor prognosis from leading AFL doctor Con Mitropoulos, who told Whitnall he would be limited in his training and that would reduce his playing prospects.

"Whilst I am extremely disappointed after receiving the second opinion from Con, I am already looking forward to the future," Whitnall said in a statement.

"I thoroughly enjoyed playing AFL and thank the Carlton fans for all their support over the years."

Whitnall said he was now considering a number of football-related job opportunities.

Carlton decided not to offer Whitnall a new playing contract following trade week last month, effectively sacking him 12 months after he won the club's 2006 best and fairest award.

At the time of Whitnall's delisting, Carlton chief executive Greg Swann said the club had been told his capacity to play would be limited because of a degenerative knee joint.

Swann said the Blues were not prepared to nurse him through a compromised pre-season campaign.

"In this day and age you have to be a hundred per cent able to do everything or otherwise you just get left behind," Swann said.

Whitnall played just 15 of the Blues' 22 matches this season and finishes his 11-year career with 216 AFL games.

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