Nic Newman, who finished behind only dual Brownlow medallist Patrick Cripps in Carlton's best-and-fairest last year, will miss the 2025 AFL season due to a knee injury.
The 32-year-old defender ruptured the patella tendon in his left knee at training on Friday.
Newman will have surgery next week, ruling him out for the Blues' entire campaign.
"We are all very disappointed for Nic and our focus is on his recovery," Carlton general manager of football Brad Lloyd said.
"He will soon undergo surgery to repair his patella, and from there he will enter into a rehabilitation program.
"Nic is the ultimate professional with an outstanding work ethic. He understands the process and will be well supported as he attacks his rehab."
Captain Cripps won his fifth John Nicholls Medal, coming after he claimed the Brownlow with a record-breaking 45 votes.
But Newman was next best for the Blues last year, finishing one vote in front of star midfielder Sam Walsh.
The former Sydney stopper will leave a huge hole in the Blues' back six as Carlton attempt to break their 30-year premiership drought.
It comes after Walsh suffered a hamstring injury at training on Monday, setting him back in his preparation for the Blues' season-opener against Richmond on March 13.
Star forward Charlie Curnow is also on a modified training program after undergoing ankle and knee operations in the off-season.
